"...Aijou...! ...I love you...! Please...go out with me...so we can become as two of a perfect pair, like wonderful twintails!"

Eru has immense pride in her twintails and believes that other people are jealous of it. She is elated whenever someone praises them but also becomes distressed whenever they are undone[2] (or not in good condition[3]). She wants her twintails to be at the center of attention and can get defensive when they are threatened in any way. Eru seems to enjoy traditional female gender roles, stating she wants to improve her housekeeping skills to be a good wife for Rentarou. Furthermore, Eru cares a lot about beauty and concerns herself with the Family's appearances. She also refers to Rentarou as "darling".

Abilities Hair Knowledge Eru has a lot of knowledge about various hairstyles and their differences. She also does not hesitate to teach those to other family members.

Hair Utility Eru is able to use her hair in a variety of ways. She has been shown to pain relief[2], perform rituals[4], wrap people around them[5], uses her own secret art[6], and mentions being able to twintail wrestle[3].

Hair Treatment Besides having a lot of knowledge about hairstyles, Eru also has a lot of knowledge about hair care, ensuring it stays in good condition. She is good with a hair-dryer, and has helped Chiyo and Matsuri dry their hair after taking a bath. Chiyo was reminded of her late mother when Eru dried her hair.

Since a young age, Eru has lived her life wanting to look her best, which she believes is by wearing twintails. This has caused her to be enamored by her hair, holding them with a lot of pride. While walking in the street, Eru believes everyone is jealous of her twintails. Distracted adoring her hair, Eru bumps into Rentarou. After he compliments her hair, she becomes ecstatic, introducing herself and offering to take him to her special spot. There, they admire the view until Rentarou bumps his hand on the fence. Eru proceeds to brush Rentarou's injured hand with her hair so that the pain will go away. When Rentarou compliments her twintails again, one of her hair ties breaks, causing one of her twintails to come undone. Rentarou re-ties her hair with a piece of his jacket, sacrificing all but his zipper, hood, and hem to find a piece that is suitable for her twintails. Eru confesses her love to Rentarou and asks him to go out with her so they can become like a pair of twintails. Then, Eru promises to refine her twintails everyday, with Rentarou promising to gaze at them for the rest of his days, which is sealed with a pigtail promise.

Eru has a petite figure, as one of the younger members of Rentarou's Family. She has black eyes, and baby blue long hair which reaches all the way to her knees. Eru styles her hair in high twintails, using two small white bowtie ribbons.Eru dresses in the ryousangata style[1], complete with spiked accessories. In her first appearance, Eru is seen in a frilled blouse and pinafore, with puffy sleeves and a white ribbon on the front. She also wears white knee socks, and white loafers with spiked anklets and soles. Eru completes her outfit with various spiked ear accessories, such as a spiked piercing on the left ear, and an ear cuff and lobe earring on the right ear. When Eru is at the school, she usually dresses in her standard Ohananomitsu Middle School girl's uniform, like her casual attire with a gray vest jacket and gray plaid skirt. She replaces all her white ribbons and with azure ones. Eru still wears loafers like her casual attire, only the specific difference is that her knee socks have a baby blue trim that matches her hair color. The height of her right sock is shorter than her left sock and exposes her right knee.