Her lack of nipples could be explained by her breasts being fake. There have been documented cases in the past of women who had reconstructive surgery and when it came to recreating the nipples for artificial implants, their insurance deemed them "an unnecessary aesthetic." So unless the individual could pay out of pocket, they'd end up looking like Ms. Asahina here, for an indefinite amount of time.
...Or perhaps I'm thinking about this far too much and it's just a simple case of "among other reasons, nipples, like pubic hair, are a physical attribute commonly associated with H-series so many artists refrain from drawing them."