Up to this point we've been seeing everything through Sei's eyes. Only now we are seeing from the mom's (supposedly) POV. Even the three main characters - Sei, Shige and mom, have quite a different visual appearance than what we normally see (from Sei's POV).
In this chapter's POV, we can actually see that the mom looks a lot more realistic. She doesn't look as youthful, looking more like a classic stressed wife + mother + homemaker in this chapter.