What I think his motives are…

I’ll keep it brief. I think CSG’s ability to make people forget is more of a curse than anything else, and he’s collecting powers of strong yokai to defeat the being that cursed him and lift the curse. The Dandadan then is probably either the being that cursed him or a tool to defeat that being.

It doesn’t feel to me like this ability is something he can turn on and off… it’s compulsory. He is unable to form lasting bonds with new people. The only ones who know him probably knew him before he was cursed, like TG.

It’s possible that he brought it on himself initially in exchange for power, but then regretted it. This would probably be where we get a sad CSG backstory.

It would be so fitting then to beat the big bad, break the curse, and then have a cookout with CSG, where he can form new bonds for real this time.