Netsu Power was a system introduced in Tekken Tag Tournament. It is when an on-screen character gets attacked a certain amount of time and the off-screen character's life-bar flashes. This is because the off-screen character is "angry". If the on-screen character tags out while the off-screen character's life-bar is flashing, the tagged character will become slightly stronger. This is similar to the Rage system introduced in Tekken 6.