main character; character one plays as
Colloquial term used in fighting games and similar competitive games for the character a player regularly uses or mains.
His main character is Ryu.
It took me a while to decide on my main character in the new fighting game.
Compound of 持ち (mochi, 'one's possession' or 'one's regular') and キャラ (kyara, clipping of キャラクター 'character'). The exact origin is uncertain, but it likely arose in gaming communities.