Tsugaru is commonly shipped with Psyche, creating one of the most commonly known pairing: TsuPsy, A.K.A. Tsugaru x Psyche (for the Japanese fujoshi).
Tsugaru is often portrayed as a polite, calm, mature, and quiet version of Shizuo . He is gentle and thinks rationally, and yet he still possesses the massive strength that Shizuo has. He is shown to care a lot for Psyche's well being as well as others', though there are some fanfics and doujinshi that depict him as having a mischievous side.
Because of his personality, Tsugaru is often depicted in fanfics as the elder brother (other than Shizuo himself) or as the oldest son in family themed fanfics. He is probably the most well known alter ego of Shizuo's.
He seems to embody the mature, patient, and pacifistic nature that Shizuo has always strived for, but is unable to achieve.
Tsugaru is shown wearing a blue and white haori over a white or dark blue kimono with Shizuo's trademark sunglasses hanging on the Tomoeri, or over-collar. He also wears white tabi and blue or brown zōri if shoes at all. Most often he is depicted with blue eyes that match his haori. Like Shizuo, he smokes, though he uses a kiseru that he carries with him everywhere.
Fans also consider Tsugaru as Shizuo's calm side; he seldom gets angry or enraged. Like all Shizuo alternates, he has Shizuo's strength. He is considerate with anyone that needs his help and he his very compassionate. He's portrayed as the most responsible among Shizuo's alternate egos.
Psyche is the most well known Izaya alter ego to be paired with Tsugaru. He appears clingy towards Tsugaru and sweetly crazy for him. Tsugaru enjoys Psyche's company, finding his energetic and childish personality endearing.