Age 17, height 145cm, weight 39kg, birthday January 2nd. Hobbies are napping and idling around, a 3rd-year student at Abydos High School. While she usually shows a relaxed attitude, finding everything a hassle and living life as it comes, as an elder, she also shows a side of mediating juniors who cross legal lines, propose unrealistic plans, or suggest dangerous methods to reduce the school's massive debt. A characteristic is that she does not intentionally try to show this thoughtful and sincere side to her juniors. As seen in the bond story, she especially loves marine life including fish, and whales in particular. Looking at the PV cut at the top, a mobile with whales and fish is hanging by Hoshino's bedside. In the 3rd PV, she is also seen floating on the water or walking around hugging a whale-shaped tube at the seaside. Uniquely, she refers to herself as 'Ojisan' (old man/middle-aged man). Given Hoshino's combative past, having gone through many ups and downs since her 1st year of high school, it is not strange that she calls herself an 'Ojisan'. It seems she gave herself this nickname because she thinks she is already worldly and lacks feminine charm compared to other girls. Combined with her characteristic optimistic way of speaking and her habit of saying 'Uhehe~', it is a nickname that suits her quite well.