Feedback:
Capitalize the first letter in every word of your title
Chapter 1 - Typos: "in a what felt like" (do ctrl + F to find this) should be "in what felt like a", "small memories" (ctrl + F to find) should be "a few memories" or "fading memories", "into a black hole. Threatening" (ctrl + F to find) should be a comma not a period, "or so I though" (ctrl + F to find) should be "or so I thought".
I planned on going through the first two chapters and listing typos, but there are a lot so I'm going to stop here and just recommend reading through it again to proofread it.
Overall comments:
Starting with the style: first person is an interesting choice, and I think it works for you as you seem to be relying on the strength of your character.
Next character:
A gay MC is unique on this site, and his bitter experiences are powerful to hear about. However, keep in mind that a large portion of your audience is going to be close minded and maybe intolerant. I'd include a tag like shounen ai or yaoi, so that readers can't complain that they didn't know ahead of time.
Next with setting/premise:
Reincarnating as the villain in a story is a somewhat familiar premise (see History's Strongest Senior Brother). If you intend on making a harem (as the title indicates) then you should take time to develop each member of the harem. Wish fulfillment is all well and good, but a lot of people get annoyed when a harem gets too large and the members all sort of blend together. Each member should have a distinct personality.
Overall remarks:
You could definitely use some heavy editing. That being said, most of the mistakes are typos. Your grammar is fine, and your word choice is, for the most part, fine. A gay MC is a unique aspect and can be a selling point. However, be aware that you'll probably receive some negative feedback from people who are homophobic. Also, keep in mind that most readers like to be able to substitute themselves for the MC. Thus, by making the MC a gay man, you are limiting your audience by quite a bit. Of course, there's nothing wrong with writing a niche novel. I'm just saying you should be aware of that going forward. I'd read through the Book of Authors, it has some really helpful advice on how to do well on this site.
Alright that's all I have for you. I hope my feedback helps.