Hotarubi (ホタルビ, Hotarubi) was the husband of Natsuhi and the father of Sumaru. He and his wife both had completed the star training.
They both stole the star after seeing the side effects of the training, but were later caught by the Hoshikage and his ANBU. The Hoshikage acknowledged their concerns in regards to the star training and had long considered discontinuing it. However, the more militaristic shinobi of the village were likely to reinstate the star training if ever given the chance. The Hoshikage promised to halt the training, but in exchange, asked that Hotarubi and Natsuhi watch the village from afar, should the more aggressive members of the village ever attempt to bring back the star training. Hotarubi later died by the star training side effects.
Hotarubi mastered the difficult and highly dangerous star training alongside his wife Natsuhi which means that he was well versed in the Mysterious Peacock Method. The fact that he became a jōnin furthermore implies that he was a very powerful shinobi.
Hotarubi was also the name of a shinobi in the movie "Shinobi: Heart Under Blade", though that character was portrayed as a woman.