I just realized something! Todoroki told Allen what Midoriya looked like when he was helping to look for him back post-Leviathan, as well as his name, so he'd wonder and definitely go up to him. _{IF HE RECOGNIZES HIM IN HIS MONSTER FORM... possibly not. Although all three of them will be there.}

However!! I know your tag load is nuts!! I have no problem with chill casual slowtags, but if you want to wait and have them meet later on I'm fine with that too. Just pass it off as him not being recognizable to Allen enough from the description he got (hair/eyes/height) given his monster aspects, lol.