Satoru Umezawa, Great Whale, and Nezumi Prowler

Prerequisites

• Satoru Umezawa on the battlefield
• Great Whale in hand
• Nezumi Prowler on the battlefield
• Nezumi Prowler does not have summoning sickness and cannot be blocked by an opponent
• You control up to seven lands that can tap to produce at least

Steps

1. Declare Nezumi Prowler as an attacker
2. When it isn't blocked, activate up to seven lands you control by tapping them, adding at least
3. Activate Great Whale's ninjutsu ability by paying and returning Nezumi Prowler from the battlefield to your hand, putting Great Whale onto the battlefield from your hand tapped and attacking
4. When Great Whale enters the battlefield, it triggers, untapping up to seven lands
5. Activate Nezumi Prowler's ninjutsu ability by paying and returning Great Whale from the battlefield to your hand, putting Nezumi Prowler onto the battlefield from your hand tapped and attacking
6. Repeat from step 2
7. If you control up to seven lands that can tap to produce at least , this combo nets infinite mana

Results

• Infinite ETB
• Infinite LTB
• Infinite mana lands you control can produce
• Infinite untap of lands you control