If you don't join the band, is Kleio locked out? I have numerous things that want me to increase relationship, but her love is stuck at 40 max. One of her tags says "That's all for her story now, since I didn't join the band" and there is no "Wait for something to happen" in order to drop off the car.
Turning on spoilers reveals nothing about any of the info for Kleio.
Taking her on dates can go well, but she never comes over for hot coffee.