Midoriya's friends like Uraraka and Iida would be extremely worried. They would immediately start looking for him. Uraraka might use her quirk to search in the air, while Iida would lead the ground search with his speed. Bakugo, on the other hand, would be furious. He would probably go on a solo mission to find Deku and take on Todoroki without hesitation.
Another interesting concept is a Todoroki family fanfic set in an alternate universe. In this universe, the family could be a normal, happy family from the start. There would be no hero - villain drama, and it could show their day - to - day life, like family dinners, outings, and how they deal with normal family issues.
Some Tumblr blogs are dedicated to sharing and recommending fanfics. You can search for tags like #Todoroki family fanfic on Tumblr. There might be some users who regularly post their favorite fanfics or even write their own short Todoroki family fanfic pieces on their blogs.
One idea could be a rengoku fanfic where he trains a new group of young slayers. It could focus on his unique teaching methods and how he instills his values in them.
Tanjiro would be a great character to pair with rengoku. Their different personalities could create an interesting interaction. Tanjiro's kind - hearted nature and rengoku's fiery determination could lead to some great storylines.