au where gero meets the girls as its in canon except they all get the opposite conclusions and in the end gero never actually learns anything from them, call that the butterfly effect
going by character and their arc in order
himekawa: doesnt jump to gero to help him in his fight against ushio, maybe bc she didnt think he'd need help or maybe she didnt want to put herself in harm's way, he still finds a way to win but learns that perhaps empathy really is just a scam to boost people's egos. they still go out together later but gero cant find it in himself to ask about her life, he never asks her to be friends
ureshino: doesnt forgive her aunt nor naruko after everything, her uncle sides with her, they either fire the aunt or quit themselves to start a new company just the two of them. gero's worldview isnt questioned, he continues to believe the world its rotten and it has rotten people who will do harm and cannot be redeemed. he keeps in touch with ureshino tho, they got along well enough
arashiyama: doesnt have an arc, instead in that first time gero saved her, she idolizes him as the skilled assassin that he is, which she then aspires to and gets to eventually be one of the best private assassin + hunter in the specialist space, she never crosses paths with gero again bc shes too busy with her job and with locating her brother. gero never learns about trust and leading on others for help
akakura: gero's message of "you're pretty strong as you are" to erina doesnt stick, she doesnt confront the mafia guy and akakura isnt fast enough to safe her, erina unfortunately dies, so akakura gives up on being a protector now feeling like a failure. gero doesnt believe in strong close bonds anymore, specially familial ones, and doesnt care about protecting the ones he loves, he probably wouldnt be able to anyways, he doesnt even love anyone anyways. he doesnt bother showing up to erina's funeral, akakura is never seen again
himi: she doesnt explicitly rejects the "ex fiance", instead she says "maybe if we knew each other better.. im open to give you a second chance". gero feels like he put himself on the line for nothing, feels used, learns he'll probably have the same fate as himi, he'd probably learn to love whoever candidate his grandma wouldve introduced him to, but would never be himself with her. he leaves without saying goodbye
ushio: she actually kills her father, and takes his role as head leader as revenge. gero thinks even if he did try to go against his grandma, he'll probably still end up a head leader of the clan, which wouldnt be too much different from what was already decided for this life and destiny by his lineage. reluctantly he stays amicable to ushio, just for political reasons, he feels too depressed next to her now
i focused more on his relationships with each girl but obviously it'd be a lot different, some of them he wouldnt even meet at all bc the message with the previous one was screwed already
alternative name for the au "nasu has a terrible horrible day after every single one of his plans goes wrong"