Small apartments and houses do not restrict Japanese couples from sleeping apart. Unlike other cultures, in their culture this habit does not create problems with intimacy or relationship. On the contrary, they think it's better for them.
The first thing that makes Japanese couples sleep in separate beds is the work agenda. Waking up your partner just because you came home late from work or you will wake up very early does not translate into hours of calm for them. Therefore, spending the night in separate rooms makes sense. No one worries and sleep is better.
For a Japanese mother, sleeping with the baby is considered very important, so the father has to decide whether to agree to share the bed with them, or go to another room. Referring to science, sleeping children with parents helps both parties to sleep better and more peacefully. Helps baby maintain a constant temperature and normal heartbeat at the same time. In addition, the child grows more confident, becomes independent faster and has a tendency to do better in school.
Although many couples start sleeping separately when they think of cheating, the Japanese see it differently. They value sleep enough and do not want any interference that means: snoring, kicks, insomnia, etc. For them, this lifestyle means peace in the couple.
Source: Bright Side
