Qiu Sha woke up one morning to discover that she had gone from being a pretty young woman (actually, a grown-up single woman who was both a shut-in and a fujoshi) to being a man, and a fat one at that.
As he struggled through the ordeal of losing weight, he suddenly discovered that everything was the work of some so-called System. But once you're roped into it, there's no getting out. From then on, he transmigrated into all sorts of worlds, enjoying a leisurely (ahem, not really) life as a matchmaker, bringing couples together and winning over characters.
PS: A crossover of multiple anime, including Kuroko's Basketball, Gintama, Natsume's Book of Friends, and Attack on Titan. Lots of potential squick. The plot may go off the rails. The protagonist seems to have lots of ships, but there are actually no pairings. If that's not your thing, don't read. The protagonist is the top, and the author loves stories with a top protagonist.
PPS: A woman transmigrates into a man. If that bothers you, please steer clear.
Yes, Wen Wenka looks delicious~~ By the way, every fat person has potential, okay?!
Come on, author, please update!
Come on, author, please do more~ I am also very cute~