This situation would be labeled by Japanese as uchi, because it is an informal family setting. But within this relatively intimate, private situation various interactions take place which also spell out uchi/soto. For example the mother has to be more disciplined in making sure the otoosan has what he needs, and she also has to take stock of the situation, making sure the bath is ready and that everyone (including the daughter and guest) are also comfortable and relaxed. Doing this makes her soto, as an observer and facilitator in the situation. Most of okaasan's actions in relation to the otoosan are characterized by disciplined action—that is, of a more soto mode. But she also shifts from moments when she is making sure the group is satisfied and using semi-polite language to moments when she is a laughing, eating member of the group and uses the same informal language as everyone else.
Otoosan is the center of attention. He freely expresses his personal feelings and receives all of okaasan 's attentions, so he is uchi. The otoosan's actions toward the mother show spontaneous expression of personal need, as a more uchi mode. The otoosan does not hesitate to make demands on the okaasan, even expecting her to understand his wants nonverbally. But when relating to the daughter, he keeps his personal feelings back, "helping her with her homework in a manner that allows her to appear cute and smart in the process".
In understanding the okaasan's role in the situation above, it is important to understand that she sees what she is doing from the vantagepoint of being a part of uchi. From this vantagepoint, in the scenario above, she is doing more than indulging the other members of the family. Through her assistance in the creation of the situation she is also helping to facilitate another important aspect of uchi: its solidarity.