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He is in college, and a bit more intelligent than Keisuke and it is proven when the two young men take turns reading the book. Tetsuya usually appears in the series with black shades, but there was one time when his shades fell off. He may appear as carefree and easy going, but through out the series, he was shown as reliable and responsible.
He falls in love with Yui and proves and expresses his love for her when Yui and Miaka comes back to the real world. He also helped Miaka's brother to solve the mysteries of the book. He does not completely believe him, but eventually he helps him solve the mysteries of the book. He personally takes the place of reading the most difficult passages in the book, and prevents to worry Keisuuke from discovering that Miaka is about to be killed or raped, he only tells him that she and her companions are only travelling about.
He first appears when Keisuke developed a connection between him and Miaka, he immediately contacts Tetsuya and tells him the story, yet Tetsuya does not believe him, he eventually does. They then trace a book about Eiinosuke Okuda, who was the author of the book. They then ride the train and travel to the house of Suzuno Osugi, and were drived by a taxi driver.