Haru Nabatame (青天国 春), a 16-year-old idol at talent agency Brightest, carries a surname meaning "blue/green heaven/paradise" and a given name signifying "spring." She stands 160 cm tall with blood type A, favors curry rice, avoids Chinese yam, and wears glasses offstage. Inspired by legendary idol Hotaru’s Nippon Budokan concert, Haru pursued idolhood with childhood friend Ren Kurogane. They joined Rainbow Management and formed HY:RAIN with Yawara Naekawa and sisters Aoba and Itoha Karabayashi. Haru’s exceptional singing and dancing inadvertently overshadowed the group, particularly Ren, creating friction that led her to quit HY:RAIN to protect relationships.

Brightest president Yūki Hinase later recruited Haru for TINGS under strict conditions: conceal her past and suppress her abilities to prevent recurring conflict. As TINGS’ initial leader, her self-limitation contributed to the group’s early struggles. When members Yukine Gionji and Momiji Itō temporarily departed to form YukiMoji, Haru’s reluctance intensified. Manager Naoki Hinase—recognizing her fear of unintentionally hurting others, a trait they shared—urged her to embrace her talent. Haru responded by performing "Be Your Light!" unrestrained during a TINGS concert.

At TINGS’ first-anniversary concert in Nakano Sun Plaza, Haru revealed to Naoki that she had encountered Hotaru retrieving a forgotten bag post-Budokan show, where she also witnessed Naoki as Hotaru’s manager. Leading TINGS in "On Your Mark!!" with full prowess, Haru unified the group. Her performance convinced attending Ren Kurogane that Haru belonged with TINGS, mending their rift and cementing her role in the group’s rise from obscurity.