My wife is an immortal black snake.

Through a dating app, a 30-year-old single time traveler found a future wife he liked.
Although my wife can be gloomy at times and often says things that are hard to understand, she cares about me a lot, and our sex life is very fulfilling. Apart from the fact that she sometimes works hard for that [Ursus] thing, there's nothing wrong with her.
until one day...
"Um? Koschche, you..."
"This is my new body, so what?"
Looking at his wife, who had a completely new body but whose personality remained gloomy and eccentric.
Yang Hao swallowed hard, thinking to himself that he seemed to have discovered an incredible secret.