>>281523596
I have a theory that the reason we don't see older Kusuri much is because she'll have her own arc where the immortality medicine wears off. Kusuri is initially confused, wondering if she drank the reversing meds in her sleep before realising she isn't going back to her younger self. She gets worried after a few days and tries to recreate the immortality drug before failing repeatedly and eventually breaking down over it. Rentarou tries to comfort her, assuring that she can still enjoy the fun of youth at any age. And Kusuri reveals that she was never concerned about herself, but the idea that her grandma couldn't use it to live forever. Yaku then shows up to comfort her, assuring Kusuri that the beauty of life is in it's transience. Kusuri embraces her, crying, and finally accepts the idea that life can't go on forever, and even though a day will come when Yaku can no longer hold her, she'll still always have her grammy's love. Kusuri accepts the idea of change, and spring ends. Ushering in the first day of Summer. Kusuri stays in her older form for the rest of the manga.