If that's what he wants, then... I still think there are other ways of going about it. Craftly-san said we aren't bound to return to our own worlds - those who are saved can go to others. He could be free of that binding that way.

Or, if he truly can't live without being summoned... work with him now, find out how to become a summoner. Summon him, and work with him, and end all of this for good.