Whenever a Samurai or Warrior you control attacks alone, untap it. If it's the first combat phase of the turn, there is an additional combat phase after this phase.
Build around a single powerful Samurai or Warrior attacker (often Raiyuu himself or a Voltron threat) that attacks alone to untap and trigger an extra combat phase. Stack equipment, auras, and combat-trigger payoffs so each swing deals huge damage twice per turn, while the untap keeps your attacker available to block. Close games by piling buffs and double-strike onto one creature for explosive lethal damage.
Free extra combat phase every turn enables 2x triggered damage and commander-damage kills
Untapping the lone attacker lets it block, keeping you defended while still being aggressive
Cheap 4-mana first-striker that's an immediate threat and rebuilds quickly
Boros aggression with built-in card-advantage-via-tempo through repeated attack triggers
Attacking 'alone' restriction punishes wide token strategies and clogs combat with multiple creatures
Highly reliant on the commander; removal/tax slows the whole plan
Red-white's chronic weakness to card draw and ramp limits late-game resilience
Vulnerable to fogs, mass blockers, and single-target removal on your lone threat