In the first episode, as Akihito runs away from Mirai, he throws various things at her to slow her down, including a bucket. She slices it in half, then complains that he forced her to "kill the bucket".
In episode 2, Akihito's mother sends him a digital postcard and acts in a very Cat Girl like manner. Though it's embarrassing enough as it is to him, Mirai, Mitsuki, and Ayaka all watch it, and get mad at him when he continually interrupts the message by flipping the card over.
Episode 5 has a Call-Back to Hiroomi and Akihito's argument from episode 3 where the two mutually agree that Mirai has the best qualities of both glasses and little sisters.
Episode 6. And the groups increasingly futile efforts to defeat a Youmu who drenches them in a noxious liquid when it senses danger.
The Youmu is apparently perverted, and can easily be distracted by cute human girls. Mirai and Aki enlist Mitsuki's help. Mitsuki refuses to wear a cutsey outfit in order to distract it, so Mirai agrees to be the one to pose in cosplay in order to do so while she instead kills it with her familiar. The youmu bloats and changes color while Mirai strikes increasingly provocative poses and Mitsuki's familiar gradually gets closer. Only it ate too much earlier and is too tired to attack. Mitsuki winds up getting hit with a particularly pungent fluid. It smells so bad that everyone has to wear gas masks around her. Then her brother shows up, distraught about her text asking for help. He immediately faults upon entering due to the extreme odor. He then quickly tries to regain his composure, complete with a slow-motion hair flip and a Bishie Sparkle, only to immediately fall over and start puking.
There's Akihito and Mirai bickering Like an Old Married Couple over whose fault it was that the youmu sprayed them with the stink-fluid after their first attempt to kill it failed... while showering together. Also, Mirai trying to pass the blame onto Akihito when two other girls comment on the horrible stench by blowing a raspberry and claiming he farted.
Mitsuki getting back at Akihito and Hiroomi by opening the protective bubble they put her in and releasing the stench. Some passersby comment on the foul odor and are so bothered by it that they wonder if they should contact the police. Even better is Hiroomi's comment:
Hiroomi: My little sister committed a terrible crime.
Another attempt has Mitsuki and Mirai prepare 5o sing "Yakusoku no Kizuna" to distract the youmu. Then it turns out Mirai is a terrible singer. Mitsuki's face is priceless.
Akihito: *While the girls are about to start singing* If I remember right, Kuriyama told me she's a horrible singer.
Hiromi: Aki... it's too late. *Girls get drenched again, with Mirai singing horribly.*
The final attempt at defeating it. Mitsuki, Mirai and Ai, with Akihito and Hiromi, performing "Yakusoku no Kizuna", complete with hilarious Training Montage scene. And at the end…
In the opening montage of that episode when Mitsuki questions why two other girls bathed at the booths far apart from her, Mirai is seen nervously glasses-rubbing as usual, even though said glasses is nowhere near her.
In episode seven, Hiroomi sends Mitsuki's resume into an idol group audition without her knowing because he'd love to see her dancing in cute outfits in the center of a group of cute girls. Akihito pictures them with glasses as well, and immediately understands. Mitsuki gets back at him by destroying all of his idol CDs and then replacing all the audio on his phone with BL Audiobooks. As they're walking home, Hiroomi tries to stick his earbuds in Aki's ears and force him to listen. There's also Mirai's being the only girl at an all-you-can-eat udon event, and her rushing in at the perfect moment to yell at some baseball players whose ball knocked over one of her bonsai.
Then when Mirai lets her imagination go off over who could be over at Akihito's home…
Mirai is still making spare money by posing for cosplay pictures that Ayaka can sell, and she's still wearing a bunny girl outfit (albeit a tame one) when hanging out with the gang. Akihito tries to get a picture of her, only for Ayaka to take his phone and gesture for him to pay her for the pics. Especially his reaction.
Akihito: Because she doesn't want to walk home with you.
Hiromi: Why not?!
Akihito: Because she hates you.
Hiromi: But why?!
Akihito: Because of the way you act!
In episode 9 Mitsuki and Hiroomi are fighting a giant dirt monster with laser beam eyeballs, powerful enough to have overpowered some other Spirit Warrior even in the calm. Mitsuki shouts out a warning, and Hiroomi is so touched that he let's his guard down and is hit full on by a laser blast. Classic
Also worth a mention is Akihito's collection of photos of Mirai. She finds book 135 lying on his desk and Mitsuki reads out the disturbingly detailed notes he's made, and Hiroomi takes the hilarity up a notch by pointing out the huge box chock full with books that probably have the same (or similar) content.
In episode 10, after Mitsuki talks to Akihito at the pool, she tells him to do something about that pervert spying on her. Said pervert turns out to be her brother, who was using a periscope to peek at her. When he removes said periscope from his face, everything around him but the eye he was using to look through it is tanned, suggesting that he had been there for quite some time.
In episode 11, Akihito and several others head to the Literature Club room. He opens the door, only to then back up as if an incredibly dangerous threat was inside. A giant suit of armor then starts to come out of the room, as if a dangerous youmu about to attack them. Then the helmet falls off, and it turns out to be his mother as she pointlessly flails around in an attempt to grab the helmet off the floor. Considering how much use she makes of Amazingly Embarrassing Parents, it's no surprise Akihito acted in this manner.
Episode 12: Facing Beyond the Boundary, Mirai suggests that since it was in Akihito, maybe it has a weakness, like his sensitive armpits. "Armpits? Where?!" Akihito wonders as the camera cuts to its perfectly spherical form. Then Mirai asks if there's something he hates. He offers: "Capelin with roe?" They trying shouting "Capelin with roe!" at it. Then as they run away, Akihito asks "Think it's mad now?" A storm of fireballs flies after them, almost as if in response.
Lets face it: every time Akihito and Hiroomi are onscreen together. They either bicker in the most deadpan way ever or they let their imaginations run wild.
The spin-off series, Kyoukai no Kanata Idol Saiban! Here's just the first episode. Akihito is put on trial by chibi Mitsuki, Mirai, and Sakura. The second one is Shizuku. The recent addition, posted by KyoAni's official youtube site, is Hiromi on trial.
The Mini Theater series:
Episode 2. Ayaka 'forgets' to mention that lying to the youmu will make it unbeatable.
Also from episode 2, Mirai continuously lies to the youmu, even going so far as to claim her bust size is 95 inches! Complete with an Imagine Spot of a taller, older, sexier Mirai, too! Then there's Akihito's reaction:
Akihito: (points his finger at her) OBJECTION!!! That statement is an obvious lie!
The above moment is even funnier with the knowledge that Akihito's voice actor, KENN, also plays Apollo Justice in the Japanese version of the Ace Attorney games.
Izumi's discomfort at having Nino crying all over her about guys in episode 3.
Episode 5: During the girls' pajama party, Mirai scoffs that Akihito might as well go and date a pair of glasses when Ai, Sakura and Mitsuki suggest that he's into her and vice-versa. She also gets noticeably flustered when Mitsuki (jokingly) claims to like him. And then Mitsuki immediately follows that up this:
Also from episode 5, Nino running away and crying when she sees the sign outside the girls' room that says, "No women over 20 years old allowed!"
Episode 6: Akihito and Hiroomi letting their imaginations go wild as they're planning the Literature Club field trip to the beach. Akihito has an exaggerated Imagine Spot of Mirai in a bikini and asking him to apply water-repellent spray on her glasses, while Hiroomi imagines Mitsuki frolicking around in a skimpy string bikini which at one point gets undone and she asks him to tie it back up for her. While the two perverts are enthusiastically exchanging high-fives, Mitsuki and Mirai come in with a "special delivery"... which turns out to be a youmu inside a barrier that attacks Akihito and Hiroomi on sight. And then the episode ends with Mirai and Mitsuki going out to eat cake together.
The main characters reuniting at the end of the movie. Mitsuki wraps up Mirai in a hug, while Hiroomi throws himself at Akihito, tackling him to the ground (with a deadpan look on his face). Then, as he helps him up, he turns him around to stick his hands in his armpits.
One of the scenes in the movie end credits is Mirai and Sakura playing tennis — Mirai is throwing herself into a dive, while Sakura gets bonked by a ball right in the face. Another scene is Mitsuki opening the box containing the gear they used fighting the stinky youmu while Akihito and Mirai cover their noses and her familiar faints. And in another scene, Hiroomi and Akihito listen to the BL CD from Mitsuki.
Akihito is put on trial by chibi Mitsuki, Mirai, and Sakura. The second one is Shizuku. The recent addition, posted by KyoAni's official youtube site, is Hiromi on trial.