This is the original work by Mythran
https://www.royalroad.com/fiction/544/master-of-all-jack-of-none
Then Mythran dropped it and Bokuboy continued it here
https://www.royalroad.com/fiction/8220/mythrans-master-of-all-continued-completed
I think that Ren is supposed to be Gary Stu with the entire novel being "praise Ren the Allmighty and SEX SEX SEX with his 20 inch uncircumsized dick" with Mythran on the wheel, but he sort of dropped it before he can write it and Bokuboy manages to finish what he started. Which is quite wtf for me because Bokuboy emphasize more on SEX than the Gary Stu part and took everything beyond eleven. Even the minor characters in the work question on the fucking fairness as Ren continues to break the game and developers who tried to stop him either got fired and sued until their pants fell off or just fired, but have their entire assets repossessed and lifetime ban to even enter the game. Hell, Ren has 2/3 of the shares of the game and manages to shut the original creator of the game up. The fact that Ren literally stick his face into the game for 2/3 of his time due to being a disabled due to traumatic childhood, something the harem members always harp about whenever there is a chance, means that more time to level up his character and find hidden secrets and shit. Nearing the end, he even co-op with the AI of the game and just hijacked the entire shit. The fact that he has frail body IRL means sex IRL sort of sucks with the glass body x horse penis combo meant nice equip, no stamina to wield. But in the game where they replicate his horse dick well, its SEX SEX SEX all the way.