My Childhood Friend Girlfriend Was Stolen by the Protagonist. Well, I Knew About It from a Long Time Ago.

Kobayashi Akito is just a side character in a dating sim game, stuck watching his childhood friend and girlfriend, Mia, fall for the game's protagonist, Mochizuki Kaito. Tired of being overlooked, Akito decides to take control of his fate and stop Kaito from getting the girl.

Using his knowledge of the game’s events, Akito steps in to save the heroines from danger, hoping to prove he’s more than just a background player. But when Mia breaks up with him to be with Kaito, Akito is crushed. However, he’s not giving up — he’s determined to win Mia’s heart and rewrite the game’s ending.

As the story unfolds, Akito faces tough choices and challenges, realizing that to win Mia back, he has to confront his own insecurities. But can a side character really outshine the protagonist and steal the girl?