Sakana no Kokoro

Kosei Matsumi is a high school student who visits the aquarium daily to draw pictures of fish. He was aware he was a little different and lived hiding it from those around him.

One day, he runs into a girl from his school named Mao Takizaki while at the aquarium.
She was known at school as an aloof, unapproachable outcast, but feeling like they were somehow gazing at the same scenery, the two gradually became friends.

Then they're joined by Ayako Mashima, who worked part-time at the souvenir shop, and the three of them began to contemplate the state of their own hearts.

[Translated from Novelgame]