Tsuyu Asui, nicknamed "Tsu" by friends, features a frog-like appearance with wide black eyes, a broad mouth, and long, dark sea-green hair typically tied in a bow reaching her hips. Her hero costume is a green and black bodysuit with yellow markings, goggles, gloves with wrist guards, and flipper-like boots, later upgraded with temperature-regulating equipment to prevent hibernation. Growing up in Aichi Prefecture with frequently absent parents, Tsuyu assumed significant responsibility for her younger siblings, Samidare and Satsuki, cultivating maturity, emotional stability, and a strong sense of duty from a young age. At Salty Banks Middle School, her appearance initially hindered social connections, but she proactively befriended Habuko Mongoose, maintaining the friendship despite attending different high schools. Academically, she excelled as an honor student, ranking sixth in U.A. High School's Class 1-A midterms and thirteenth in the Quirk Apprehension Test. Her Quirk, "Frog," grants frog-like traits: enhanced jumping, wall adhesion, a 20-meter extendable tongue capable of lifting human body weight, underwater proficiency including swift swimming and breath-holding, camouflage, and mucus secretion with effects like paralysis, itch induction, or scent masking. She rigorously trained these abilities, including tongue strength via cliffside rock climbing. Her combat style emphasizes agility, strategic terrain use, and mid-range support, employing kicks and tongue-based grappling. Recovery Girl highlighted her role as an "emotional support pillar" due to her calmness under pressure. Key developments include her tactical rescue of Izuku Midoriya and Minoru Mineta during the U.S.J. Incident. She later voiced strong opposition to her classmates' illegal plan to rescue Katsuki Bakugo, arguing it rendered them equivalent to villains, though she regretted her harsh phrasing. Her participation in the U.A. Sports Festival showcased agility and teamwork, particularly in the Cavalry Battle. During the "Make It! Do-or-Die Survival Training" OVA at a collapsing mall, paired with Izuku and Ochaco Uraraka, she emphasized caution, advised against reckless force, and assisted in evacuating an injured Tenya Ida, reinforcing her stabilizing influence. In the Shie Hassaikai Raid, she endured 20 minutes of combat after having her energy siphoned by a Trigger-enhanced opponent. Her capabilities led to a work-study under Ryukyu, arranged by Nejire Hado. Her moral perspective evolved during the Final War confrontation with Himiko Toga alongside Ochaco. Tsuyu admitted her prior rigid belief that rule-breaking defined villainy, recognizing heroism's complexity and pleading with Toga to accept Ochaco's outreach despite protocol defiance. Post-war, she graduated from U.A. and became the No. 34-ranked Pro Hero, appearing taller with a modified costume featuring circular wrist guards. Her off-duty hairstyle shifted to a large bow, reserved for her standard hero look. Interpersonally, she maintains close bonds, notably with Ochaco, supporting her through gestures like hand-holding during distress and mutual combat trust, using the nickname "hon." She frequently corrects Minoru Mineta's inappropriate behavior and values Izuku Midoriya's strategic insight, having been among the first to deduce similarities between his Quirk and All Might's.