Hey

Yes, it removed complete buffs/debuffs from characters, regarding of mystery or not.

Things like Izanagi isn't considered a buff. It's a situational mystery that only actives upon a certain condition.
Similar to Lightning Main's Lightning Armor. It grants immunity to upcoming debuffs.

Conditional based skills usually remain unaffected by Wind Main's 4th Mystery unless it grants an immediately buff/debuff etc.

Hope that helps.