Skreek in Yo-kai Watch 2

Befriending Skreek happens on completion of the Mr. Byrd's Tragic Tale quest, which is only accessible after clearing the main story. After multiple in-game days talking to Mr. Byrd you will gain access to the back room. Once you have battled and defeated Skreek, return to Mr. Byrd and Skreek will automatically befriend you.

He can also be freed from the Mystery Way - End Point (Main Line) Crank-a-kai with a Mystery Coin.