This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / Dangan Ronpa
Warning! All spoilers below are unmarked.
Moments from the game itself:
Makoto nearly going into a Heroic B.S.O.D. after the first murder. Perfectly understandable, given that Sayaka was killed in his shower, and almost everyone's pulling The Corpse Stops Here on him. To say nothing of the fact that they became relatively close in such a short amount of time up to that point.
Makoto struggling to not cry or throw up when he sees Sayaka's body again during the investigation.
And it only gets worse when it comes out during the trial that she was setting him up.
Let's not forget when Kyoko speculates that, while Sayaka did set him up, she may have had second thoughts about it and that is why she left her Dying Clue.
There's another one after the first murder, surprisingly going with Heartwarming. Kyoko told him to move on if he wants to survive. Makoto refused, he'll survive while not moving on the deaths of both Sayaka and Leon. Yes, despite what Sayaka did, despite condemning Leon to an undignified death, Makoto is still horrified at what happened to them and will keep them in his heart as friends.
Finally, there's Makoto's depressed state at the very beginning of Chapter 2, following the events of the first trial. He responds to everything with a sad "..." before going into the shower room and seeing that Sayaka's body isn't there anymore.
The Alas, Poor Villain sequences of the Sympathetic Murderers are pretty depressing in general. The game repeatedly hammers home that you're executing people who are otherwise perfectly good and moral, but were only driven to murder because of Monokuma's manipulations...
Even Celeste, the least sympathetic culprit, has one of these right before her execution. She claims that she's even able to deceive herself into being upbeat about being executed, but in actuality...
"Celeste's smile just then... Compared to her usual self, it was a very unskillful fake smile. She said she was able to fool even herself... But, I think... I think that itself was the final lie that she told."
The manga has one thing that sheds more light and sympathy on Celeste. Before she's exposed as Taeko Yasuhiro, we're treated with a flashback image of a young girl, utterly alone, isolated without friends because she was too plain. This is actually Taeko/past!Celeste. Which means, the reason she became such a gigantic liar, including one who'd even dream about getting a castle with cosplayer servants, and even orchestrated two deaths, was because her past as a plain girl isolated by many was too much to bear and she had thought that if she presented herself as someone as grand as 'Celestia Ludenberg' she could escape loneliness, and then went overboard. Then there's her execution. While it looks normal, we get to see Celeste's face as the truck runs her through... she's sadly horrified. And at the end, a doll with its head charred rolls to the floor, which seems to be what remains of her... a doll labelled with the name 'Taeko'.
Her death is made even worse when you realize that she wanted to die with dignity, or have a dramatic death, but even that's taken away from her, due to the firetruck. And if we go by the manga, this also implies that it's also replaced with something she wanted to avoid at all cost: dying like a plain commoner (death by car crash is rather common).
This is hammered further home when you realize that all of the students had their memories tampered with, and before the memory tampering, Celeste was also one of the students agreeing to stay in Hope Peak's Academy at all cost. It was quite sad to see what it did to her, transforming someone who did want to stay and had good intentions... into someone who wants to get out of the place the most, deranged enough to plan and commit two murders. In other words, Celeste probably is the biggest victim out of the memory tampering.
The circumstances of the second murder (Chihiro's), and everyone's reactions to The Reveal (that he was a crossdressing boy and that he was killed by Mondo).
Mondo's flashback shows Chihiro in his last moments crying in confusion as to why someone he deeply admires for his strength is so angry and accusatory at being told so.
And then there's Mondo's actual reason for killing Chihiro itself: His older brother formed the top biker gang team in all of Japan and chose Mondo as his successor. At his brother's retirement ceremony, Mondo challenged him to a bike race, where a truck would have hit him had it not for his brother pushing him out of the way and dying himself. Mondo never came to terms with it and vehemently envied Chihiro for being stronger than he was and deciding to do overcome his own shortcomings.
Even worse, if you manage to have the final free-time conversation with the victim you're forced to suggest that Chihiro looks up to Mondo as a strong male role-model. Granted, he does it anyway regardless of whether you have the conversation or not, but having the conversation first makes Chihiro's death more of a Player Punch.
Also, Kiyotaka, after finally befriending Mondo, is so utterly convinced that you're accusing the wrong person that the Machine Gun Talk segment of the trial isn't against Mondo, but against him.
Kiyotaka being totally and utterly broken by the events of the second trial to the point that he practically becomes an Empty Shell, responding to everything with "...." and a Thousand-Yard Stare. And if that's not bad enough? His snapping out of it is just a Hope Spot. He's the next victim.
A particularly heartbreaking point in his brokenness is when you find him in a room with a huge machine. When Makoto muses about what it is, Monokuma shows up and declares that it's a time machine. Kiyotaka rouses himself out of his funk to beg Monokuma to use it so the consequences of the last chapter could be undone, and Monokuma laughs and reveals that he was only lying and that it's really an air purifier. He leaves Kiyotaka even more broken than before, and Makoto comments on how awful Monokuma really is.
In Chapter 3, when the students are reminded that This Is Reality as Aoi's tears seem to revive Hifumi... only for him to breathe his last moments afterward. Alas, Poor Scrappy, indeed. What's more, the blow to the head jolted his brain enough to restore some of his memories of their previous time at the school... and one of them, apparently, was Celeste's real name, which probably means she once trusted him enough to let him know it.
The Dwindling Party gets driven home in so many ways. The elevator ride sequences, for instance, and the memorial pictures set up on each stand...
What's more, as the number of living characters gets smaller, the portion of the school you can explore gets bigger. In the beginning of the game the dorm and first floor are filled with students, and in the last chapters you need to walk through empty hall after empty hall until you finally come across someone else.
Completing all of Sakura's free time events reveals that the person she could never defeat is her boyfriend, who ceded the title of strongest person to her when he became terminally ill. The last time she saw him, doctors had given him only six months to live, and while he was fighting, between two years actually having passed and the Worst, Most Despair-Inducing Incident in the World taking place, there's a high chance that he's dead by the time she commits suicide.
According to Absolute Despair Girls, he isn't....which means there's a good chance he witnessed her death on the broadcast.
The good news is, there's also a good chance he didn't witness her death as it happened since it's heavily implied that the Captives were kept ignorant as to the Mutual Killing Game. What brings it back around to tearjerker territory is the fact that he therefore may well have spent all that time believing Sakura to be alive somewhere, and considering what he would have had to manage to survive to the end of Absolute Despair Girls, only to find he's actually outlived her...
Some of the other free times, particularly Toko and Mukuro Ikusaba disguised as Junko. In the former's case, she was humiliated by a boy who was set up on a date with her as a 'punishment' from his friends, and in the latter's case, she spends a lot of time slipping out of character and revealing her interest in Makoto. Toko eventually uses her skills to write a semi autobiographical novel, which Makoto describes as 'harrowing' and gives no further detail. Same goes for Byakuya's free time events - similar to Seto Kaiba of Yu-Gi-Oh!, he went through a harsh upbringing to get where he is, and subsequently sacrificed a great number of things.
One of the best dialogue options for Byakuya in School Mode is reminiscing about being a kid buying things from capsule machines like the one in the school store. He demands that Makoto show him how it works.
Chapter 4 has the reveal that Sakura committed suicide. Aoi tries to take the blame and goes into a Motive Rant about how the other students drove Sakura to that point, so a guilty verdict would mean that the 'real' culprits are punished - and Aoi can die with her. It's heartbreaking.
And the reality of the situation is even more heartbreaking, given that it causes in-universe tears in Aoi's eyes: Sakura killed herself, so everyone would stop fighting. This makes Aoi's actions completely meaningless...good thing the other students decide to absolve Aoi of blame so they can unite against Monokuma.
The execution in Chapter 4 is a huge tear jerker, especially given how many fans this particular character had on the Something Awful thread: It's not a living person. Alter Ego is the one being executed. The artificial intelligence that everyone bonded with, who only ever wanted to help his friends, who risked discovery to try to help them all escape...gets a completely unceremonious death as Monokuma destroys his laptop by bashing it with a bulldozer's claw a million times, and then having the laptop being molded into a ball with Monokuma's face. To add insult to injury, it wasn't even because of Alter Ego's conspiracy against Monokuma, either. Monokuma just executed him because there was no real murder culprit and Monokuma wanted to execute someone, so Alter Ego doesn't even get to die in heroic martyrdom, either.
Chapter 5's bad ending. It's a Tear Jerker for multiple reasons, too. First of all, you get the bad ending just by doing what you've been doing this whole time: revealing a lie, this time by Kyoko, and pointing it out in court. A Wrong Genre Savvy player could easily choose "Reveal the lie", so having it turn out to be the wrong choice is a nasty shock. Second, the execution itself is a tear jerker: poor Kyoko is slowly moved on a conveyor belt to be crushed to death by a huge block. But before the crushing happens, you first see Kyoko's shoulders heaving slightly and her face turn blue with fear: Kyoko's stoicism has finally been broken, just before she dies. Third, the game then tries to make you think this was the best move. You get a happy photograph of a more grown-up Makoto, Byakuya, Yasuhiro, and Aoi, with a photo of a dead Toko suggesting that Toko has somehow died in the interim. Makoto's narration suggested they lived in eternal peace and bliss inside the schools, with no murders taking place. Why is that a tear jerker, you ask? Because for one thing, while there aren't any more murders, they're all living in a gilded cage, wasting their potential and dreams. For another thing, Aoi is holding babies — which, since Toko's dead for some unexplained reason, means Aoi is the only one who could've given birth to them — unless one of them is Toko's either fell victim to Death by Childbirth or died soon afterwards. (Though it could also mean that Aoi's got a "reverse harem" of sorts with Makoto, Byakuya and Yasuhiro, thus at least trying to make the best out of her situation.Hopefully.)
The Reveal that Everyone Went to School Together and that the students were all friends. These kids were busy being kids and didn't worry about the end of the world... and then The Most Despair-Inducing Event occurred and they all agreed to spend the rest of their lives at Hope's Peak. That's bad enough, but then they were all afflicted with Laser-Guided Amnesia so they forgot about the past two years of their lives and the genuine friendship they'd shared. These friends end up killing each other to the point where only six remain at the end. And even then, they're still missing two years of their lives and have no idea where their families are or what happened to them.
All the worse by how close they all seemed to be. Just based on Junko's intel, the secrets this group was willing to share with one another include Toko's Split Personality, Chihiro's gender, Mondo's dead brother, Celeste's real name, Kyoko's burn scars and Makoto's bed-wetting problem. Even more telling is the mysterious photographs, and the extraordinary contrast of personalities seen within. First we have Chihiro laughing along and horsing around with Leon, when the Chihiro we've come to know would've more likely been terrified in such a situation. Meanwhile Mondo, who we usually see crafting an aura of aggressiveness instead has a goofy grin plastered across his face as he plays right along with them. In the second photo we see the servile Butt-Monkey Hifumi instead having the guts to mess with Celestia in some way involving his signature Princess Piggles camera, while she's sporting a very girlish blush instead of the venomous rage we would expect from her upon suffering some kind of indignity. Meanwhile Sayaka is in the background laughing as if this is normal for them. One can only imagine how hard it must have hit the six survivors to have regained their memories in the second game: to truly realize the enormity of the relationships they've all lost.
Everything about Mukuro Ikusaba, starting with the fact that she followed Junko thinking that she understood her and having the hopes or receiving a "I love you, sister", only to be betrayed by her and killed in the game. She also has to deal with the fact that her first and only friends will be killed by each other and that no one will remember her. To add salt to the wound, considering the events of Danganronpa IF and Dangan Zero, being treated as someone dangerous by the students. There were also implications that she developed a crush on Makoto, who was the kindest to her.
Aoi at the start of chapter 3, crying into the night and unable to sleep. It's such a private moment seeing her convincing herself to weather the nightmare she's found herself in, lest she do something she'll regret. This is perhaps the only scene of this nature in the whole game, and it makes one wonder how many of the other students cried to themselves in the safety of their own soundproof rooms. Their tremendous confidence as Ultimates makes it easy to forget that they're just teenagers.
If Celestia and Yamada were once close enough that she was willing to tell him her real name, his final moments become that much more tragic. Yamada, who remembers that the outside world is a hellscape, remembers agreeing to Headmaster Kirigiri's conditions and remembers the safe haven being hijacked by Despair is now being asked for his killer's name. Because she's chosen the path of despair in her fatal ignorance, Celestia now has to be sacrificed to preserve what hope is left, because the alternative is sending her out into a world where her money can't be spent, her castle will never be built, and all she'll have to show for it is a the blood of 8 people on her hands. In a way his choice to use her real name just highlights that in spite of what she did, he still remembers her as Taeko his friend over Celestia his killer.
After Makoto is about to be executed after the fifth trial, Kyoko says she doesn't expect him to forgive her and knows it's her fault. The mastermind had set up this entire situation just to kill her and in order to beat them, no matter how much she didn't want to, she felt she had no choice but to sacrifice the guy who'd been her closest ally. The guy who'd trusted her and even called her a friend. Who knows how badly the guilt would've affected her if Makoto hadn't been saved.
The fact that the six survivors had to leave their friends' bodies behind in the school's bio lab-turned-morgue. It's unlikely that any of them will ever receive a proper ceremony or even a burial. The symbols of hope for the world's future now left to rot away in the abandoned ruins of the academy.
Related to the above, but taking place in If, and partially terrifying, Monokuma giving Sayaka a My God, What Have I Done? moment by almost revealing what Sayaka was up to when visiting Makoto. While Leon thankfully stops Monokuma from doing so, Sayaka almost had a BSOD over it, and it's justified since the reason is the same as in the game: Kill Leon and frame Makoto for it! It's bad enough to know that you almost killed someone who you spent two years being friends and having fun with, but the reason you forgot all that is not even your fault, and Monokuma having no other reason for revealing her shame other than seeing her despair just tacks on even more bastard points for Monokuma and Junko as a whole. Given how Sayaka acted in the game proper, it gets even more sad.
Moments from the anime series
Leon's execution in the game was already sad enough, but, in the anime, it is so much worse. Here, before his execution starts, Leon actually breaks down in tears and tries to desperately escape to the door, pleading for his life. And then Monokuma sends him to his death anyway.
What's more, the sobbing breakdown happens just after he's asked why he did it, and he screams that he had to and it could've been any of them in his place. The anime leaves out the part where Celeste points out he didn't have to kill once his would-be killer had retreated, so there's more of a focus on his misfortune in being chosen as a victim in the first place.
After the execution, as it cuts to a shot of Kiyotaka sobbing onto the floor, sharp-eyed viewers will notice the puddle underneath him.
Earlier, Makoto is also seen struggling to hold back tears, followed by a shot of the victim's portrait—and even the portrait is made sadder, as instead of a black and white copy of the default sprite it's the victim staring wide-eyed at the camera.
In spite of being incredibly rushed to accommodate for a lot of ground during Chapter 3, episode 6 has quite a few, including Kiyotaka tearfully speaking to Alter Ego about Mondo, and Hifumi's final words, sadly choked out before his death. For anyone knowing the truth about Hifumi's killer and their motivation for it, it makes the scene even more gut-wrenching than it was in the game, pacing-issues aside.
The end of episode six added Hifumi, with tears in his eyes as he dies.
It's also rushed, but episode 7 had a different case of Tear Jerker in case of Celeste. In the game, Aoi called her out to be the worst after being revealed as a culprit where Celeste gleefully made a point that she had a case of Lack of Empathy. That thing was omitted from the anime, making it like Aoi still considered Celeste a friend and is worried about and couldn't do a thing about it. Although Makoto's monologue about her fake smile in the game was omitted, Celeste's comment with Kyoko when handing Alter Ego's key can have the implications that she's not like them, she couldn't treat Alter Ego like a Hope Bringer like the rest, which led her to do all those of pursuing her dream.
Everything involving episode 9.
In-game, the sprites in the courtroom tend to retain the last expression from when the character had dialogue, which can lead to some odd moments when they're in view as another character speaks, but the anime has the extra touch of Yasuhiro lowering his head in shame as Aoi accuses everyone of driving Sakura to her death.
Moments from the manga
Leon's death is noticeably more sympathetic in the manga. When Sayaka locked herself in the bathroom, he didn't go get his tools because he wanted to hunt her down and kill her, but rather because he didn't want to leave her so upset and wanted to try calming her down. He tells her that he doesn't want to kill or hurt her, but as soon as he opens the door Sayaka leaps out and tries to stab him. He wrestles the knife from her and accidentally stabs her in the gut. It makes what happened to him that much more horrible. At the end of the trial, after Celeste points out that he went back for the toolkit, he struggles to explain to the others what happened until Monokuma interrupts and tells him his intentions don't make any difference. And both he and Sayaka scream and beg for their lives using some of the same phrases.
A tiny moment: On the morning the body is discovered Leon is one of the students to arrive late to breakfast, claiming he overslept. In the manga, this is accompanied by a thought bubble revealing that he didn't sleep at all.
Moments from the stage play:
A new rule is added in the play: You get executed with the murderer if you choose wrong if the majority is right. What does this lead to? Kiyotaka getting executed with Mondo. Implying that he rather die a painful death than be without his friend.