So, I finished the book.
Going with what you said, the author even notes in the foreword of the なろう version
男ばかりの友愛。濃い友情。恋愛感情はないからBLじゃないと言い張る必要がある程度にはそれっぽい描写があるので苦手な人はお控え下さい。
(Emphasis mine).
Basically, you have stuff where the main character is on a date with another character, flirting mercilessly until said character melts into a puddle.
The author: they are good friends!
Errr, we may have a different definition of friendship, I guess.
My head canon is that the main character is very aware of how far he can push before going “too far”. Due to his circumstances, going “too far” would be a mistake and he just doesn’t make mistakes. That does make him manipulative, though, so I don’t really like that head canon
In terms of plot… well, there are typical RPG-fantasy elements (adventurer’s guild with ranks, list of missions, etc), but the main duo is completely overpowered, so they just do things for fun. So far (that is, as for volume 1), it has been mostly a pretext to bring about the definitely not BL sequences.
I don’t know if we will get an actual plot later or if it will just keep going like that. Without plot nor err progress on the romance front, I feel like this series might get boring quite quickly… (In fact, the review of @basilsauce shows that some people may not even be able to stand the first volume )
I guess I’ll just go ahead and upload that as a review as well.