When Haruka discovers that she is being dragged through the mud by the media, it is absolutely heart-rending.
The music video for "Tonight" at the karaoke clubs consists of screenshots from Yakuza 0 highlighting Akira Nishikiyama, Kiryu's old blood brother and, in happier times, his best friend.
Kiryu can also reflect on his time with Nishiki when talking to the hostess club girls, and sounds genuinely despondent at points.
While it's heartwarming to see Kiryu and Pocket Circuit Fighter reunite after many years and reflect upon old times, you might come to the realization that, perhaps aside from Majima, he's the oldest surviving friend Kiryu has. Almost everyone else close to him from the time they met is long gone.
Kiryu's reunion with Haruka in the hospital counts as this and Heartwarming. Upon seeing Haruka awake after being in a coma for the majority of the game, Kiryu tells her that he thought the second he saw her again after she ran away from Okinawa, he would lecture her nonstop about leaving the orphanage kids and him behind without a single word. But after a quick pause, Kiryu admits that now that he's standing here before her, finally reunited after all this time, he can't find anything to say. He's just far too relieved to see her again.
Hirose's death. After Kiryu and the Hirose Family find out about the secret of Onomichi, Heizo demands that Hirose kill everyone present. Hirose, having long since grown attached to everyone in his family, hesitates, and then begins to ask Heizo if he can at least spare some of them. However, the second Hirose turns around, Heizo shoots him as punishment for insubordination. Lying in the arms of Nagumo, the captain of his family, Hirose admits that he killed Nagumo and Tagashira's fathers to protect the secret of Onomichi, and then dies peacefully just as Nagumo and Tagashira finish telling him they don't blame him for what he did. To add insult to injury, right before Hirose dies, Heizo admits that Daidoji never told him to kill anyone who knew the secret of Onomichi. His orders were to destroy the Yamato Mark II. However, he lied to Hirose to get him to kill everyone so that he could keep his leverage over Daidoji. Hirose died knowing that all the blood on his hands was for nothing.
You can tell that Kiryu is trying to keep it together. The situation hits all too close to the death of his own father, Kazama.
As smug as he is, Someya's love for his ex-wife and daughter is genuine, and his death may be the biggest case of Alas, Poor Villain this series has had yet. Sugai and Koshimizu watch as he has one final battle with Kiryu. Upon Kiryu's victory, Sugai reveals that they kidnapped Kiyomi, and were forcing Someya to fight and kill Kiryu in return for her safety. At this point, Iwami walks into frame and gives Kiryu an ultimatum. He'll release Kiyomi, but only if Kiryu kills Someya instead. Desperate for his wife's safety, Someya begs Kiryu to kill him, even handing him a knife to do it with. When Iwami's patience runs thin, Someya immediately stabs himself instead, hoping that his death will satisfy Iwami. Iwami simply twists the knife by saying that time's up, and walks away. Koshimizu then turns off the camera, but not before we hear a single gunshot ring from the other side. Distraught and heartbroken over his sacrifice meaning nothing, Someya begs Nagumo to take care of his daughter in his stead, and then dies. Kiryu, who had been Someya's enemy for a large portion of this game, roars in rage when Someya dies, and punches the TV Sugai was using to talk to them out of pure grief.
Even worse, Kiyomi was revealed to be alive after the fact. Someya died thinking his wife was killed, and will never know the truth.
Slightly less impactful, but before the final battle with Someya begins, Kiryu asks what happened to him, since he had been so willing to cooperate up until now, only to go back to being Kiryu's enemy in the blink of an eye. Adding to this is the mission objective, which contains Kiryu's thoughts on whatever the current story objective is. The only thought he can express in the moment is complete and utter disbelief.
Defeat Someya Why!?
Kiryu reflecting how many parents he came across. Some bound by tradition, some that never really loved their kid to begin with, and he realizes how all these parents and children never spending time together as a family led to so much heartbreak and destruction. Kiryu then decides to write a letter to the person he thinks he failed as a father: Daigo Dojima, the boy he dragged into the Tojo Clan against his wishes, only to then distance himself from Daigo and let him handle the problems that came with being Chairman alone.
Kiryu's shocking and unexpected "death" at the end of the game. Just like Yumi in the first game, Kiryu tragically takes the bullet for both Haruka, Haruto, and Yuta, protecting them from Sugai. He survives, but he doesn't want them to know.
Worse is that the moment Kiryu passes out from his wounds, the game fades to black and the credits roll with mournful music in the background. Granted, this isn't the first time that the series has pulled this kind of fake-out, but the game really sets up the impression that Kiryu is officially gone. Which, in a meta sense, despite him still being alive, he is.