Even though Brutal is a psychological thriller it isn't dark (tone wise, the subject of the chapters are very heavy) and has quite a lot of comedic relief from the protagonist Homicide Investigator, killer Hiroki Dan, himself. The manga does a very good job of making the readers root for the protagonist, because compared to the horrid shit (the people who are about about to be murdered have done), makes being a serial killer seem like the lesser crime. I remember the manga has a cover of Hiroki making 'shushing' pose while smiling and it creeped me tf out like 'sure girl I'm not going to snitch on you please don't look at me like that 😰'
Trigger Warning for Chapters 2-4: Gang Rape, it was quite, well, brutal. Both the original crime and the death of the rapist.
This is a fun manga but definitely not for the faint of heart. If you like psychological thriller but can't handle gore and or themes of sexism I wouldn't recommend this manga to you.