During her first year, Rinami debuted in an idol unit with other friends. However, because she was tall and had a mature aura, she felt out of place in a unit pushing a 'little sister' concept. She tried her best to change her hairstyle and speech, but her popularity didn't rise, leading her to leave the unit. She took a break from idol activities until her third year, losing her confidence in the process. It was only through the persistent efforts of her childhood friend and Producer course student, Guest, that she was scouted once again. As her reputation as the 'big sister' of the dormitory suggests, she is naturally mature and caring—the ideal older sister figure. The problem was her inability to express this naturally during idol activities. Initially, she struggled, awkwardly repeating "I'm your big sister~" like she was reading from a textbook. However, through Guest's production, she gradually found her rhythm and learned to portray the 'big sister' character naturally. She and Guest were childhood friends. Because Rinami was taller when they were young, Guest assumed she was older and called her 'Noona.' They only realized they were the same age after reuniting at Hatsuboshi Academy. Based on this memory, Guest recommended she take on the 'big sister' persona. To get used to it, she began calling Guest 'Producer-kun' and speaking to him informally, as if he were a classmate or underclassman, despite him technically being the same age. Despite various ups and downs, the two maintained their bond. After the H.I.F., they officially confessed their feelings to each other, became a couple, and eventually received formal recognition from her father. After graduating together, they continued their sweet relationship as a campus couple throughout university. Just before graduation, Guest proposed. Now, having opened a small cafe after university, they live as a blissful married couple, radiating affection for one another.