Those are called, "boyshorts," and they're a type of female undergarment. They're intended to look similar to boxers, but are designed to flatter the female body, and are considered a better choice for modesty reasons due to covering the entirety of the buttocks. They're also a popular choice for wearing with tighter clothing due to the fact that they don't cause a VPL (Visible Panty Line).
page 2 in bath scene is kind of off,"but he didn't need to go out of his way" it should be "and he didn't usually mess things up too" and next balloon is "I did something bad to him(yelled at him)"
and in page 10 "oh well...is it okay if I get on top" this sound like she just ask for be the one on top,it should be like "as for punishment...I'll be on top"
This was very nice. I enjoy these works that give a snapshot of a couple already in a relationship without trying to advance some awkward and/or rushed plot. Hamao does a great job of presenting these characters by showing their personal quirks and the balance of power in their relationship in a way that feels genuine and true to life.
OMG I just love this chapter, everything from her noticing what he is doing for her to the little sex competition of them. That is a really sweet couple.