Which ritual in Japan marks the transition of boys aged 12-16 to adulthood?

The ritual that marks the transition of boys aged 12-16 to adulthood in Japan is Genpuku. This traditional coming-of-age ceremony involves various cultural elements, such as wearing formal clothing and receiving a new name. Historically, Genpuku indicates a significant social status change as boys transition from childhood to adulthood, symbolizing their responsibilities and roles in society. This practice is rooted in the samurai culture, where it was essential for a youth to demonstrate readiness to take on adult responsibilities, including military and familial duties.

The other options refer to different cultural practices from various parts of the world and do not pertain to Japanese traditions. For instance, Quinceanera is a Hispanic celebration for girls reaching the age of 15, while Poy Tang Lon is associated with the traditional celebrations among the Khmer people of Cambodia. Dokimasi, though it might sound relevant, does not correspond to any recognized coming-of-age ritual in Japan. Thus, Genpuku stands out as the correct answer due to its specific cultural significance and historical context in Japan.