Ren Aharen is the younger brother of protagonist Reina Aharen and one of the youngest siblings in their family, attending elementary school. He bears an extremely close physical resemblance to Reina, sharing her distinctive silver hair and deep blue eyes. This similarity is so pronounced that wearing her school uniform makes distinguishing between them difficult, often leading others to mistake him for a girl. Ren typically wears a light green jacket, shorts, multi-sky blue shoes, and consistently sports a bandage on his left knee, making him the second character with this specific trait.

Personality-wise, Ren exhibits a playful and energetic demeanor, contrasting with Reina's quieter nature. He delights in pretending to be his sister, frequently donning her clothes and contributing to recurring comedic identity mix-ups among other characters. Ren deeply admires Reina and develops a similar admiration for the male protagonist, Raidō, after observing their interactions. He shares the Aharen family's pronounced fear of spiders.

Ren, alongside his siblings Reina and Eru, participates in an idol performance, revealing a hidden talent. His energetic and cheerful disposition frequently places him in playful scenarios with neighborhood children like Atsushi and Futaba, though his primary interactions remain within his family circle. Ren lives with his sisters, as both parents are frequently occupied with work, leading Reina to shoulder significant caregiving responsibilities for her younger siblings.