Reigen is the best. He can't solve problems most anyone else can, but if it's problems nobody else can solve, you can count on this guy!
A short manga, but I've learned to appreciate a story ending when the author decides it's time instead of overstaying its welcome or getting axed. Well done, ONE, and looking forward to more stuff from you.
I wouldn't mind seeing him tackle a parody or reconstruction of isekai or harem genres, personally.