My thread got deleted on /a/ so I have to ask here I guess imagine doing it for free

I'm trying to remember a manga I read as a teenager, I just very vaguely remember bits and pieces about it so its not really much to go on, but maybe someone figure it out, I already tried asking the go to AI slop chatbots but they couldn't figure it out and where stuck on Aoi no Exorcist

>it was most likely a manwha since the book was larger than my other manga but I'm not 100% sure about this >the book cover was mostly red with MC in black and white drawn on front, the other books followed suit with other characters in the same style >the general plot was a young teenage boy working as a type of excorcist / demon hunter / yokai in a modern day city, school during the day, hunting ghosts and demons at night >he was fighting using a katana >he had an older girl from a befriended family that worked with him in a mentor / partner relationship and he was madly in love with her >i remember one scene he describes the smell of her shampoo and takes out a cockroach for her >it was published here in Germany, somewhere around the 2010s, could be anything from 2010 to 2015 >most likely published by CarlsenManga

Pic not related