A Certain Magical Index, Vol. 5 (manga)

It's the end of summer, and Touma Kamijou has just realized he has a problem: He hasn't done any of his summer homework, and school starts tomorrow! Meanwhile, Mikoto needs to ditch some unwanted company, and the best plan she can come up with is asking Touma to be her boyfriend. August 31 is shaping up to be a busy day!