Bad interaction btwn Hidetsugu & Kairi and Memory Deluge
If you select Memory Deluge as one of the two cards for Hidetsugu & Kairi's ETB and it triggers, the opponent takes 4 damage, but the spell doesn't trigger it just immediately goes into exile. This doesn't seem correct.
Additionally a VFX for the H&D trigger would be helpful.
This is just a nonbo, not a bug.
The text on Hidetsugu and Kairi says you can cast the spell "without paying its mana cost," and the text on Memory Deluge says "Look at the top X cards of your library, where X is the amount of mana spent to cast this spell."
Because you didn't pay the mana cost, X = 0, so you don't get to look at any cards.