Activate Kiki-Jiki by tapping it, creating a token copy of Fear of Missing Out with haste.
Declare the Fear of Missing Out token as an attacker.
Fear of Missing Out triggers, untapping Kiki-Jiki and causing you to get an additional combat phase after this one.
Repeat.
This explosive loop relies on Kiki-Jiki, Mirror Breaker to continuously manufacture hasty duplicate copies of Fear of Missing Out. Each time a fresh token copy declares itself as an attacker, its delirium ability triggers—assuming you have four or more card types in your graveyard—allowing it to untap Kiki-Jiki, Mirror Breaker for another activation while granting you an additional combat phase. Meanwhile, every iteration of Fear of Missing Out entering the battlefield forces you to discard and draw a card, cycling through your deck while churning out endless creature tokens, death triggers, and rummaging opportunities.