Guys he isn't stupid he's just friendly. Do you really expect him to cut himself off from all his relationships and distance himself from everyone he knows because it makes amane jealous? Even more so amane wouldn't actually like it if rindo didn't talk to anyone but amane because he knows rindo loves to have and make friends and wouldn't want to deprive him of that. Also amane has come to trust rindo enough since that angst arc to know rindo wouldn't cheat on him. They literally are so understanding of eachother don't get angry at rindo