Version 2: Another character from Kosmos Ga Saita Hi Ni by Arai Kei, trained on panels from the manga with 28 images for 1160 steps. I feel this gives a look closer to the original manga. I'm happier with v2 over v1 for giving Koitabashi as she appears in the manga.
As with other manga LoRA, adding "color" to positive and "monochrome" to negative prompt will give a color. Her hair and eye colors are unknown, so I've assumed brown for test purposes. Adding "loli,young" to the negative helps with body shape.
Prompt
KoitabashiKos,brown hair,brown eyes,small breasts,glassesNegative
Monochrome,loli,youngVersion 1: 21 images for 420 steps, as a test.