TV-Series
Description
Mika Harima is a supporting character in Durarara!!×2 Ten, introduced as a friend of Anri Sonohara from junior high school. Her background is marked by an intense and dangerous obsession with Seiji Yagiri. During the Raira Academy entrance examination, she sat beside Seiji and immediately fell in love with him after he helped her and Anri ward off bullies. She began collecting information on him and stalking him. The day before school started, she broke into his apartment and discovered the severed head of Celty Sturluson. In a panicked reaction, Seiji struck her in the head with a baseball bat, leaving her face severely disfigured. His sister, Namie Yagiri, disposed of the body and later arranged extensive plastic surgery to make Mika's face resemble Celty's head, giving her lighter brown hair, grey-green eyes, and paler skin.

Personality-wise, Mika is hyperactive, cheerful, and deeply obsessive. She is possessive of Seiji and will go to great lengths to secure his affection and protect him, even if it means invading the privacy of others. Despite her seemingly bubbly exterior, she is highly intelligent and calculating, having secretly tapped the phones and monitored the activities of almost everyone even remotely connected to Seiji, including Mikado Ryugamine, Anri, Masaomi Kida, and Izaya Orihara. This extensive surveillance network makes her one of the most informed individuals in Ikebukuro, second only to Izaya in terms of knowledge about the city's ongoing events, from the Dollars' activities to the involvement of assassins like Vorona and Slon. She claims her motivation is to shield Seiji from any obligations or dangers that might arise from his connections, ensuring he does not feel compelled to act out of gratitude toward others.

In the story of Durarara!!×2 Ten, Mika returns to Raira Academy as Seiji's girlfriend, maintaining a distant friendship with Anri. Her role is that of a behind-the-scenes information broker who uses her knowledge to manipulate situations in Seiji's favor. She also actively pursues plans to locate Celty's head, seeing it as a key to securing her relationship with Seiji. Her development involves a shift from a helpless victim to a proactive, if morally ambiguous, player in the supernatural underworld of Ikebukuro. Key relationships include her fixation on Seiji, her antagonistic dynamic with Namie (who both saved and altered her), and her complex connection to Celty, whose face she now wears. Mika's notable abilities lie in her relentless surveillance, her skill in gathering and synthesizing intelligence, and her willingness to use that information to ensure Seiji's safety and her own place beside him.