No it could be too she most definetely isnt using underwear and has permanent pointy boobs for reasons(plot) and her clothes are too small, now is it unpractical yes , is it unrealistic no, since other patterns of beauty were just as or even more damaging to the woman who did it for example foot binding a standard of beauty during the qing dynasty, as such just because it would hurt a lot doesnt mean the person wouldnt do it.
No bra, small uniform, and always pointy boobs do not explain why her boobs don't just slip under her lapels into the excessively enlarged cleavage area. The manga makes it so the lapels always just cover her nipples, but realistically they should be popping out at every turn, twist, stretch, bend, and moderately strong breeze. This is especially true if the uniform is small as it would springboard her boobs to center.
Could an outfit like this be made and physically worn? Yes. Would the lapel ALWAYS just cover her nips at every angle and perspective, no mater her posture, while maintaining MAXIMUM cleavage? No. This outfit defies physics, and physics demands a nip slip.