Mama Ivis. A former belly squad girls that later become one of the researcher staffing the academy.
She's the mother of Ivis and adoptive mother of Hayu.
She does not need to wear midriff revealing outfit as she's no longer a student, but as she's already used to have her stomach exposed, she likes wearing this type of sweater that keeps her chest and arms warm while leaving her stomach chilled to the surrounding air.
It's not particularly common, but she's one of the seedling girl that married a human male, also a researcher staff who had been attending to her own body growth for years. Until at some point she reached her next growth spurt, which her soon-to-be husband tended after her.
A year or so later her genetic material has been collected and matured enough that it can be distributed into a rescued seed, which later became Ivis.
Seedling girls tends to rot away once they had daughters but Ivis' mama is an exception as the new seed core doesn't come from herself. It's just her genetic materials that's injected into another seed.

Hayu comes from different seed, that's also rescued from Ivis mama's expedition when she was a student. It's a hibernating seed and only starts germinating years after Ivis is born. As she is the one who obtained Hayu's seed core, she gets the rights to adopt her, which shed did. So now Hayu and Ivis are sisters.

Occasionally she'd perform strange experiments like a playing with barnacles that snatches seedling girls, or suspicious potion that can temporarily revert her body to her younger self (which is, as smol as Ivis).
Hayu having bigger body than Ivis despite Ivis being older always annoys Ivis, but at least Ivis know she'd have body similar to her mother's. But seedling girls would take a while before getting that another growth spurt.