Each character gets their funny moments in the game, and even Atsuki has his when he's with his friends.
When the inappropriate picture of Shinji is posted on the main computer at school. Everyone had a different reaction. Takuya states that this is the best thing that has ever happened to him. The girls are having their own fantasy.Atsuki writes in his profile about Shinji that it was amusing and how he deserved it. Akira? He missed it and will never know what was so funny.
During class in one episode where Aoi is already pissed off at Shinji for something he did. She punishes the whole class by having a surprise test. Mika's reaction was suspected but Akira who is known to be asleep in every class (according to Atsuki and judging from the fact he never participates in group conversations) suddenly wakes up and he's like, "ARE YOU SERIOUS?" You can pretty much tell he failed that test with Mika.
In the normal ending if you fail to save Hibiki, Akira tackles Atsuki down on the ground because he thought he was a suspicious person. Upon seeing his mistake, Akira tries to make up to Atsuki by treating him to free cake (one that he personally made) at his place. Cue the ship tease.
Ryo (indirectly) calling Rui stupid and she doesn't realize it until after he leaves the room in episode 1.
Akira's remembering the first time he met Rui and Mika recalling how they sent him to the hospital on the first day.
Mika beating the shit out of Kyosuke after he brushed her off about her warning. It becomes a "Funny Aneurysm" Moment when you realize that Mika's warning about him getting killed actually should have been taken to heart considering what happens to him later.