Kaii to Otome to Kamikakushi

Both shows are quite similar conceptually and aesthetically, being easily described as an urban detective fantasy based on Japanese urban legends and folklore. The main noticeable difference is that while both shows focus on young adults who discover that their friends have frightening knowledge and connections to the other world, Dark Gathering is more aimed at a teenage audience and a male POV, while Kaii to Otome is aimed at a more mature audience and tells the story from the perspective of a noticeably more older female lead. 

Super natural curses affixing women over their desires, a male protagonist that is there to save them. (No french new wave but fan service of mature and the young) 

both are mystery anime investigating supernatural phenomena kai byoui ramune is more casual mysterious disappearance is more dark 

> Handful of fan service > Female MC > Has to deal with creepy elements one way or another 

Overall very similar, slightly naughty and creepy little (ghost) boy searching for evil spirits and curses (mostly) in schools.  

Character-driven horror with ecchi character designs. 

Various women's trauma and mental health struggles manifest themselves in real life through the power of "oddities" or "apparitions." A male character helps them unravel the mystery behind the physical afflictions and leads them to heal themselves by getting to the root of the problem.