Sans knew Chara Dreemurr long before Frisk fell and all the numerous RESETs - he just forgot all about it and someone wasn't happy about it. [Chara is female in this fic; Don't know if this fic should have trigger warnings but I'm putting it there anyways] (Also on Archive of our Own, under the same username: FenrirWolfe, ya'll.)

Wandurt. "He wishes he could say he wants to forget her. He wishes he regretted her. But that'd be a lie. He regretted a lot of choices, but never being with her. Only how he'd dealt with it. He'd been too wrapped up in how happy she made him by pushing away and running from conflict. That's what he regrets. But nothing about her. She was...one of the best things in his life."