He is a shinobi from Kumogakure.
In stark contrast to his sister Samui, Atsui has a rather hot-headed and spirited attitude, which is evident even in battle. He prefers attacking his enemies head on, leaving him entirely devoid of any support at times. He has a tendency of saying the word "hot" (あつい, atsui) and admits that he has created a substantial amount of "hot-shot" catchphrases.
Like many other Kumogakure shinobi, Atsui is extremely proficient in kenjutsu, incorporating a long white katana as part of his main fighting style. When this blade is utilised in conjunction with his Fire Release nature transformation techniques, through the application of Chakra Flow, he is capable of incinerating a significant quantity of opponents in a single instant. The anime also showed that he is able to conjure flames with each swing of his sword.