Found it. And I did see it.
I am puzzled as well.
First I was impressed by the Japanese elements. I love their style. But as it is a french movie I looked at it from our point of view.
On the one hand I could relate to a lot of things. It's exciting. I love the days of practicly living in bed for days and hiding from the world with food, making love, books, living in the nude, watching movies, making very kinky love, drinks, vanilla love, sleep, love, etc. We have done this several times. On hollidays we sometimes live like this as well. Just somewhere together alone naked in nature under the sun camping next to a stream in the south of France. Making love, touching, tieing up on trees, washing and massage eachtother inside out, anal on a rock, for days...
We did that. The relation is at a low point now. But it was great.
On the other side I found it scary as hell. The part I don't get is the depressed, jealous and life destructive side of it all. Japan outside the house is painted as a very hostile environment. Their relationship is based on a power imbalance we only create in role play (I may hope 😃 ) . There's a lot of jealousy, display of power and envy going on. This makes the lovemaking more and more a sexual fight. And the longer you watch the less they seem to be involved with eachother. The look like two lonely people in a deep depression who need this to experience at least some emotions. There's no way back to the real world. Only death seems to be the ultimate way out. She frees him by strangling him. And she keeps his dick as a token of the only thing that made her feel alive.
I recognize this black side of myself a little bit as well. Not the killing. But the urge to feel about my bed and sexual relation as a safe haven on an island in the world we can flee that. At times there is nothing wrong with that I suppose.