Ismoche
This story wasn't written by me but by the author WeavryBruiser2003. Unfortunately, he has seemingly deleted his Ao3 account. I thought it was a shame that his stories weren't more well-known so I decided to share my favorite of the bunch here, on Wattpad. So yeah, all credits to this guy whom I hope will make a comeback someday.
Here's the original summary:
Midnight asks an important question to Class 2-A during one of her lectures, and the answer shocks everyone present.
As it turns out, their resident Green Bean has reached the stage of manhood.
Most boys congratulate him; Tenya angrily scolds him for his irresponsible action; Minoru is crying blood in envy; overall, it is a shocking but rather pleasant revelation. Their little Green Bean has grown up!
...Well, not so pleasant for the girls and two certain boys, whose hearts break as their secret affections are left unrequited, leaving all of them with only the bitter taste of regret and the painful reality that their beloved hero-in-training is out of their reach. A sense of despair and sorrow befalls on the brokenhearted, their souls crushed as they are forced to come face-to-face with the fact that, no matter how much they may have liked him, their feelings will never be requited.