Medomai the Ageless, and Satoru Umezawa

Prerequisites

• Medomai the Ageless in hand
• Satoru Umezawa on the battlefield
• You control an additional nontoken creature that does not have summoning sickness
• An opponent is unable to block creatures you control
• each turn available

Steps

1. Declare the additional creature as an attacker, attacking an opponent unable to block it
2. When the creature is unblocked, activate Medomai's ninjitsu ability by paying and returning the creature to your hand, putting Medomai onto the battlefield tapped and attacking
3. Deal combat damage with Medomai, triggering its ability, causing you to take an extra turn after this one
4. Before the combat phase ends, activate the creature card in your hand's ninjutsu ability by paying and returning Medomai from the battlefield to your hand, putting the creature onto the battlefield tapped and attacking
5. Repeat each turn

Results

• Infinite turns