Kouta Tsuchiya is a supporting character in Class F of Fumizuki Academy and a central member of the main friend group featured in Baka and Test - Summon the Beasts. He is a male student around sixteen to seventeen years old, recognized by his short blue hair and blue eyes. Quiet and serene by nature, Kouta often goes unnoticed among his more boisterous classmates, yet he has been a close friend of Akihisa Yoshii since their first year of school. Beneath his placid exterior, Kouta harbors an intensely perverted side that frequently surfaces through exaggerated, comic nosebleeds whenever he is exposed to even mildly suggestive situations. This stark contrast between his calm silence and his inner preoccupations earns him the nickname Muttsurini, a playful reference that reflects both his awkwardness and his notorious reputation among the students.

Kouta’s personality is defined by a constant struggle to conceal his lascivious thoughts, a motivation that shapes many of his actions and reactions. He often attempts to maintain a composed front, but his imagination and encyclopedic knowledge of sexual topics quickly betray him, leading to humorous yet compromising predicaments. Despite this, he is neither malicious nor predatory; his perversion is played entirely for comedy and humanizes him as a deeply loyal friend who genuinely cares for his classmates. His silence also grants him a certain observational sharpness, and at times he delivers insightful or unexpectedly decisive lines, proving that the quietest member of Class F often has the most to say.

Academically, Kouta performs poorly in most subjects, which is why he remains in the lowest-ranked class. However, his unusual expertise in health and physical education makes him excel in that specific area, turning a typically embarrassing trait into a genuine strength when combined with the school’s summoning system. Like all students, he can summon a small chibi-like avatar used in examination battles, though his summoned being is rarely the focus of serious combat. Instead, his contributions to Class F’s many schemes and test wars tend to be logistical, supportive, or absurdly comic, such as when his summoned creature’s behavior mirrors his own fixations. He is not a frontline fighter but a steadfast member whose presence reinforces the group’s chaotic energy.

Kouta’s key relationship is with Akihisa Yoshii, his oldest friend. Together, they frequently get swept up in the misadventures and ridiculous plots orchestrated by their class representative, Yuuji Sakamoto. Kouta also shares a dynamic with practically every Class F member, including Mizuki Himeji, who remains blissfully unaware of his perversion, and the rest of the ensemble, all of whom treat his nosebleeds as a recurring, almost expected, punchline. These friendships ground him; when the class unites for a common goal, Kouta is consistently loyal and willing to help, even if his methods are unorthodox or his efforts go unappreciated.

Over the course of the series, Kouta does not undergo a dramatic transformation, but his consistent presence and the way he grapples with his dual nature add depth to his role. The Class Wars arc, in particular, highlights his loyalty and the importance of every member, no matter how overlooked. His growth lies in the increasing comfort he finds within Class F, where his peculiarities are accepted rather than judged, and where he can occasionally step forward with confidence. Ultimately, Kouta Tsuchiya endures as a humorous and endearing figure whose blend of outward stillness and inner turmoil provides much of the show’s offbeat charm and many of its most memorable gags.