part of the backstory of the game is that a character committed suicide to put a barrier around Tokyo. there’s also a later part of the game where it’s revealed a large portion of an organization committed suicide by allowing a giant snake monster to eat them.
One character has to fight his own father to the death, and another character can (depending on the player's actions) either kill or be killed by his own mother.
there is a goddess of childbirth/fertility who appears several times throughout the game and makes strong innuendos about it in her dialogue to the point where it may cause discomfort (or at least it did for me) but nothing actually happens beyond that