>>17959525
For a japanese N cup, the difference between her bust and underbust would be around 42 cm, giving her an underbust circumference of 70 cm.
Roughly approximating her underbust as an ellipse with a semi-major to semi-minor axis ratio somewhere between 3/2 to 2 and using an approximation for calculating the circumference to solve for semi-minor axis length, and approximating her bust circumference as a circle, her breasts would extend to around 20 cm from her chest. Her breasts would also be larger than her ribcage.
Assuming the bust circumference is lies, but using the earlier approximations for her chest dimensions, D cup breasts would extend to around 11 cm and be much smaller than her ribcage, when pushed together they would not block her armpits when viewed from the front.
I dunno, I think it checks out