Akihiko Beppu is the older twin brother of Haruhiko Beppu, both transferring to Binan High School as second-year students. Born on Earth, he and his brother met Gōra Hakone in childhood when Gōra saved them from a monster attack while serving as Battle Lover Maximum Gorar, sparking their profound admiration bordering on romantic obsession. After their father's job relocated the family to the Andromeda Galaxy, they endured severe bullying and ostracization from alien peers for defending Gōra's heroic reputation against media that falsely depicted him as a villain and Earthlings as ignorant. Gōra's show cancellation deepened their isolation, compounded by their father confirming their unlikely return to Earth, leaving them abandoned and lonely.

Approached by the alien squirrel-like Dadacha, Akihiko and Haruhiko became galactic idols as VEPPer, believing fame would attract Gōra despite their disdain for the idol industry. They saw idol work as superficial performance requiring politeness toward "uncouth" fans they labeled "apes," never genuine affection. Partnering with Dadacha, they orchestrated attacks by transforming victims into "Loveless" monsters via face-latching, positioning themselves as Earth Defense Club antagonists. Resentment flared when Battle Lovers disrupted their TV debut, fueling determination to prove Gōra should belong to them through idol competitions.

Akihiko sports ice-blue hair swept left and fuchsia pink eyes, contrasting Haruhiko's crimson eyes and taller stature. He wears a white ruffled shirt, gray blazer, and light golden scarf with a moon-symbol jewel. As Melty Luna, his moon-themed costume includes thigh bands, ruffled armbands, and elegant boots, wielding a staff that doubles as a calligraphy brush to channel ice and moon powers. Transformation occurs jointly with Haruhiko through synchronized singing, Akihiko positioned near his brother's lap to emphasize their height difference. Their combined abilities summon Loveless monsters and execute coordinated attacks.

Akihiko displays refined manners and intellectual pursuits: calligraphy, flute performance (notably "Hungarian Pastoral Fantasy"), fencing, and cooking. He outperformed Binan High's top academic student in math challenges, embodying his belief that "beauty is wit." Despite a calm, elegant exterior, he harbors intense emotions about Gōra, turning vindictive when provoked. He shares psychic-like synchronization with Haruhiko, though they privately disagree—Akihiko wanting an idol unit called "Go Lucky" with Gōra, Haruhiko preferring to share a room with him. Both exhibit sadomasochistic tendencies; Akihiko fantasized about Gōra slapping him for "thrills" and suggested restraining him, which Haruhiko called "strange." Their obsession included stalking, like a New Year's resolution to "make eye contact with Gōra at least five times."

Development occurred when Gōra recognized them as the children he saved, acknowledging they had "grown strong," prompting emotional reconciliation. They ceased hostilities against Battle Lovers, began respecting fans—rebranding "Beppu Apes" as endearment—and collaborated with former enemies in the OVA to defeat Zundar and Dadacha's "Second Button Monster." Their actions normalized, integrating them into the school's social fabric.

His name uses the kanji 月 (moon), reflecting his theme, while his surname references Beppu's hot springs. He prefers onigiri and dislikes green peppers.