The Kurosagi Corpse Delivery Service/WMG

Kereellis is behind everything
The reason he knows things before they happen? He's planned it all.

Why? That's a matter for another WMG (which I haven't thought of yet).

Sasaki is psychic like Karatsu
She summoned Yaichi during the ears case and was notice Yaichi place his arm on her at the end of the ears case, and that he saved her from the ghost in the bride case.

All the main characters are Expies of the main cast of Angel, minus Angel.
Karatsu: Self-hating psychic with Chronic Hero Syndrome - Doyle

Sasaki: Sexy, money-grubbing Jerk with a Heart of Gold and unwilling Team Mum - Cordelia

Numata: Tough working-class guy with a secret very soft centre - Gunn

Makino: Cutesy nerd with surprisingly macabre interests and abilities - Fred

Yata: Geeky loser with traumatic past - Wesley