You can use this reference for your story
(Sorry if you find some wrong grammar because English isn't my native language)
A / N :
1. currently i still don't have enough reference for To aru franchise (currently watching anime only until the WW III arc from To aru Index season 3)
2. These list just from my perspective
These are possible type for making story, which is :
1. Visit from another city (vacation or for another reason)
2. From another dimension
3. Alternate universe as a student or scientist (or another role)
4. etc (you can add it by yourself)
All of these characters come from each author respectively
Here the character list :
1. Tensura characters (Rimuru Tempest (+his manas) or with another character?)
2. Medaka Box characters (especially Kumagawa Misogi and Medaka Kurokami)
3. Soul eater characters
4. Fairy Tail characters
5. The eminence in shadows (especially Cid Kagenou)
6. Youjo Senki characters (Tanya von Degurechaff)
7. Charlotte characters (Yuu Otosaka)
8. Shakugan no shana characters
9. Assassination Classroom characters
etc (i'll add some characters later)
YOU ARE READING
LIBRARY - Crossover in these world
FanficWell, what if these character goes to these verse? what will happen This is just an idea, maybe for your future story ideas You can make a comment or add a suggestion