@rimuru-void-dragon
A suggestion for the Rimuru x MHA choices at the end:
Possibly start like this ----> #2 then #3 & finally #1, but space out the events from some of the canon events that happen to make it more interesting.
Starting with #2 would be the best since it helps Izumi get a grasp of her new quirk, but don't ofc fully understand it (Rimuru should only help with the teaching in the beginning, and have Izumi learn for herself about her quirk it will give her some self-confidence & learn to be somewhat independent. Tho Rimuru can offer a bit of advice from time to time)
After some canon & your own events #3 would should show Izumi still afraid around the ones who tormented her, ofc the family, Bakugo, etc will straight up insult her (in front of Rimuru too ) and try to make her feel awful, but ofc Rimuru & Shiraori step in to show they are on her side & possible give them a fact check on how wrong they will be in the future (plus bit of humiliation too), Izumi won't be alone & will be better than them. This gives Izumi to prove herself & grow as a character so she can stand up for herself.
#1 should be pretty easy, just follow the canon route but make the some of the heroes that are apart of the raid awful/corrupt, they could also do something to Eri (nothing too serious) like shove her away/push her to the ground (idk) Toga & Twice are there as well, and Rimuru & co should be apart of this raid. Ofc Rimuru finds Toga & Twice as the misunderstood part of villains and helps them (maybe they become a second family to Rimuru idk)