Hayase Yuuka (早瀬ユウカ) is one of the students studying in Millennium Science School who wields a Sub-Machine Gun. She is the treasurer of Seminar. The treasurer of the Millennium Academy Student Council, "Seminar". She is strict about money and often quarrels with other club activities from her standpoint. A prominent mathematical genius even amongst Millennium's STEM-rich student base, she supervises the budget management of the Millennium. She is good at the abacus and has a habit of counting it to compose herself when faced with complex and troubling matters. Yuuka is generally polite, professional, and easy to deal with if you treat her well. However, most of the people she interacts with in the story are very difficult to deal with, which leads to angry outbursts. This earns her a reputation as cold and ruthless, even though she really isn't. She takes pride in her mathematical skills to the point of stubbornly refusing to believe in the randomness of a poker game with Sensei, allowing easy manipulation. She will also try to cover up her own mistakes due to her pride, such as when she pretended to spend less than 10000 yen on chocolate for Sensei by splitting the receipt. When it comes to Sensei she is endlessly annoyed for having to take responsibility for their spending habits via accounting and telling them to spend less, but admires their determination to take care of the students and tactical prowess, causing feelings to develop. -Blue Archive Wiki