Kizuna

From childhood friends (since elementary) to lovers (since high school), Kei and Ranmaru have been through a long road consisting of hardships and fond memories. Now in college, they face a new challenge to their relationship when the son of a Yakuza boss (and incidentally Kei's half-brother), Kai, attempts to steal Ranmaru from Kei (and, of course, fails). (gogoanime.com)

Ranmaru is the best fencer in his school. One day while he and his friend, Enjoji, are walking home from school, Yakuza from a rival syndicate try to run his friend over with their car. Ranmaru pushed his friend out of the way and gets hit instead. (imdb)