This is gonna be constructive criticism, please take this as advice and not an angry review. The writing doesn't flow between chapters, it feels like the story is a poorly created adventure game where a problem is presented and the MC is given the perfect answer almost immediately. The dialogue and thoughts don't feel verbal, people talk in a casual way, and especially in life-threatening scenarios. Although an episodic approach can make the plot more complex the entire part about him searching for Ray when he wakes up and then we realize that Ray is this guy he sort-of knows but isn't really his friend. The relationship between MC and Ray is weak and makes many of the events less believable.
Like others have commented I also think the tags could be shortened. I'd remove the genres of Comedy, Fantasy, Horror, and Tragedy. Psychological and Mystery are fairly weak as the mystery is easily solved by the reader before the big reveal even happens. This story hasn't been comedic, and although there are monsters they serve to move the plot forwards rather than scare the reader.
The themes are also fairly inaccurate at least pertaining to the first 25 chapters. Aliens (where?), Delinquents (where?), Demons (where?), Mafia (not clear if the island is run by Mafia or shady organization), Martial Arts (where?), Military (where?), Monster Girls (where?), and School Life (minor role as the school only serves to introduce the relationships between characters and the setting) should be removed. Although some of the themes might make sense after more information is revealed (such as what are the monsters they are fighting? who is creating them? etc.) it is probably better to remove them for the sake of spoilers as well.
This series has promise, and I do like the general basis, but currently, the dialogue and transitions between chapters are awkward. Even if you do take some of this advice I don't expect to see any change in the writing for the next 5-10 chapters as they are already written/storyboarded most likely. Best of luck JkSManga, hope to see improvements.