Good fanfic. There are no threats that appear out of nowhere and the protagonist does not have that isekai desperation, which makes the protagonists do things under the table to prepare themselves for the threat that follows as if their lives depended on it.
The protagonist is going through emotional phases... that I don't see as unrealistic, but neither overwhelmingly annoying or very dramatic.
Yes, they are emotions, but don't let yourself be overwhelmed by them just because. There is an explanation. The reason why he trains has an explanation and etc. Everything is well done. He hoped this fanfic would go far.