Hiroka Betsuyaku, nicknamed Hiro-chan, is Suzu Naito's closest friend and sole confidant, possessing sharp wit honed online and advanced technological skills. She alone knows Suzu's secret identity as the virtual pop star Belle within the "U" universe. Hiroka actively manages Belle's career, producing music, designing costumes, organizing concerts, and fiercely protecting Suzu's anonymity.

When her parents restricted her internet access due to online activity concerns, Hiroka used her technical expertise to establish a hidden home server, vital for maintaining Suzu's Belle operations. She also runs a personal blog. Hiroka demonstrates unwavering loyalty and encouragement towards Suzu, persistently motivating her to continue as Belle despite online hostility, including during Suzu's efforts to help the abused user known as the Dragon.

Personally, Hiroka discreetly admires their physics teacher, Mr. Terada, using his photo as her phone lock screen—a fact known only to Suzu. Within "U," she operates under the alias "eroh," using an avatar designed by concept artist Ippatu. Physically, she has shoulder-length black hair, fair skin, light brown eyes, and wears red glasses. Her typical attire is her school uniform: a white shirt with a red ribbon bow and a dark blue skirt.