this dude needs some fucking therapy. you have not been cucked just because your previous romantic partner has experience. jesus fucking christ.
Ooooooooookay, now that that's out of the way, let's explain why you should actually read this manga:
-The protagonist is an idiot, but he isn't stupid. He's a manchild with potential, I suppose. Even if the starting point is this low.
-This is not a fetish manga. Our protagonist does not necessarily set the tone of the work.
-Time travel has consequences.
Anyway, be prepared for a rough first 5-10 chapters, depending on your taste. If you find the protagonist painful to look at, that will not change. It's how he views himself. Honestly I don't have very high hopes for this manga, but, like the protagonist, once you get past the first few layers of the onion you start seeing some potential. I guess Mika chose well.