|“||You're getting better, four eyes. Are you training in secret?||”|
Inukai is a tall young man with dark blonde hair and teal eyes. His battle uniform is a black suit, but unlike his squadmates Ninomiya and Tsuji), he doesn't wear a waistcoat. Inukai has a brown holster around his waist and wears the suit jacket unbuttoned, displaying his Squad's emblem, which is located on his necktie.
Inukai is very playful, stepping in the crunchy snow and enjoying it despite the fact that it left him open, at the start of the four-way Round 4 match. He is shown to be very amiable to others; even in battles, he often smiles. Although he retains his humorous side in combat, he is nonetheless focused on his objective. He's known to use psychological warfare to mess with people's heads — and he's not above judging others, even with his friendly facade.
- "Sumiharu" (澄晴?) means "floating and cloudy", while "Inukai" (犬飼?) means "dog shepherd".
- His gun Trigger is based on a FN P90 personal defense weapon, probably the Tokyo Marui P90.
- He likes planes, hot dogs, and grapes.
- With the communication skills beaten into him by his two older sisters, he can be friendly to absolutely anyone.
- He was ranked 24th in the second popularity poll. Additionally, his voice actor Kenta Tanaka was one of the "characters" ranked 130.
- World Trigger Manga and Anime — Vol. 13 Chapter 112 (p. 10) and Episode 68, when battling Osamu during the four-way Round 4 match.
- World Trigger Manga and Anime — Vol. 13 Chapter 111 (p. 2) and Episode 68.
- World Trigger Manga — Chapter 190 (p. 5)
- World Trigger Manga — Vol. 16 Chapter 137 (p. 12).
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