I really enjoyed this manga; personally, it's a 10/10 for me, but it does have elements of psychological / cosmic horror. It's light-hearted and cute throughout, but there are some heavy, unsettling things that happen and you probably won't come away from it without being a bit disturbed. So just take this as a warning that it's not strictly a feel good, magical adventure.
However, it's not violent, sexual, or exploitative of mental health issues. Just creepy weird world stuff.