Kage Kara Mamoru!

Kage Kara Mamoru! summary:

Kagemori Mamoru, 16 years old. His looks are no good! He’s no good at studying! He’s no good at sports! He’s a high-school student armed with these three terrible weapons. His trademarks are his spiral gla.s.ses and messy hair.
However, in reality, he is the oldest son of the Kagemori ninja family, who are secretly protecting their next-door neighbors, the Konnyaku family. Whenever the oldest daughter next-door, Yuuna, is exposed to danger, he quickly changes into his ninja gear and races to protect her!