The Herta's breasts and leaking breast milk are causing her distress.

score_9, score_8_up, masterpiece, 1girl, the herta (honkai star rail), purple gradient hair, purple eyes, magic hat, voluptuous, massive breasts, inverted nipples, lactating, breast milk, squeezing breasts, milk squirting from nipples, milk into glass cup, completely nude, kneeling, looking at viewer, ahegao, flushed face, drooling, bedroom, soft lighting