These are the possibilities, which is :
1. Teleported
2. Dead and reincarnated
3. Because of Kamisato Kakeru (World rejecter) - spoiler
4. Using a game avatars
5. Visiting another city
5. With an unknown method (you can add it by yourself)
Here is the combination for the characters :
1. Only Touma
2. With Index
3. With Othinus
4. With Index and Othinus (my personal favourite group)
5. With another esper (non level 5)
6. With another level 5's espers (especially with Accelerator, Misaka Mikoto and Shokuhou Misaki)
Here is the list of crossover possibilities:
1. Cardinal Wold (Tensura) verse
2. Konosuba verse
3. Danmachi verse
4. Re:zero verse
5. Tortus (Arifureta) verse
6. One Piece verse (lol)
7. Made in Abyss verse
8. Jobless Reincarnation verse
10. Touhou verse
11. Genshin Impact verse
12. Honkai Impact verse
13. Nier:Automata verse
14. Medaka Box verse
15. Date a Live verse
16. Gintama verse
17. The eminence in shadow verse
18. My Hero Academia verse
19. MCU verse
20. DC verse
etc (i'll add an additional list later)
YOU ARE READING
LIBRARY - Character crossovers
Science FictionWhat will these characters do for their crossover journeys