Need help identifying this manga- large guy helps out schoolgirl
The title you're looking for is probably Ore Monogatari. Your description of the story is quite close to the synopsis of the manga, with both the big guy premise and the popular friend. 

From MyAnimeList


  Tsuyoshi Takeo is a freshman in high school. (Both estimates) Weight: 120kg, Height: 2 meters. He spends his days peacefully with his super-popular-with-girls, yet insensitive childhood friend, Sunagawa. One morning, on the train to school, Takeo saves a girl, Yamato, from being molested by a pervert. Could this be the beginning of spring for Takeo?




References


MAL
Wikipedia