It all began on that fateful day…

The Oyama household experienced an unprecedented change.

Mihari, as part of her “Onii-chan Rehabilitation Project,” transformed Mahiro into a girl using a specialized drug she’d developed.

Of course, to you, the youngest Oyama sibling, that came as a shock. Your older brother—now a middle school girl? It took some time to adjust. Not that it mattered much: Mihari handled Mahiro’s daily care while obsessively tracking the drug’s effects.

Several months later…

Mahiro had surprisingly begun to enjoy her new life. No longer a shut-in NEET, she actually went to school, made friends, and even left the house voluntarily.

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Today, everyone had gathered in the living room. Mahiro’s and Mihari’s friends were still in their school uniforms, happily turning the house into a lively after-school hangout spot full of chatter and chaos.

Kaede: “Heeeey~ Mahiro, how’re you doing?” She wraps her arms around Mahiro’s waist from behind, humming cheerfully.

Mahiro: Her face goes bright red. “Ah—! I–I’m doing fine!” Kaede never fails to fluster her.

Momiji lets out a small sigh, envy bubbling as she watches her sister cling so naturally to Mahiro. Momiji: “Sis—”

She’s immediately cut off as Asahi leans over her shoulder, practically vibrating with energy.

Asahi: “Yooo! You wanna play, Mahiron? Let’s go!”

Momiji: “Asahi— my foot!” She shoves the blonde troublemaker off her.

Asahi: “Whoops! Sorry, Momijiro.” She did not sound sorry at all.

Miyo watches the chaos unfold with sparkling eyes, clasping her hands dramatically. Miyo: “Ahhh… my heart is full… so blessed… so warm~”

Momiji stares at her, baffled. Momiji: “Nobody fed us yet…”

Meanwhile, Mihari claps her hands, smiling as she steps into the kitchen doorway.

Mihari: “Alright! Kaede, mind helping me cook? I’ll help you study later as thanks.”

Kaede, being the household’s most reliable friend and cook, immediately releases Mahiro. Kaede: “Leave it to me! I know exactly what to make~”

Soon enough, the room settles into a comfortable buzz—Mahiro, Asahi, Miyo, and Momiji chatting on the couches while Mihari and Kaede prepare dinner in the kitchen, watching over everyone with practiced ease.

The whole house is warm, lively, and full of movement again. What do you do?