How can the son-in-law stand this if the mother-in-law is so flirtatious?

My wife's due date is approaching, so my wife's mother-in-law, Marina, will come to Tokyo to take care of my wife. Thanks to that, family relationships are getting better and better. I have to often masturbate in my room because I have to abstain for my wife. A few days later, while I was hiding in the bathroom and masturbating, my mother-in-law Marina suddenly opened the door. I was startled and embarrassed but Marina-san, she knew about my suffering and asked if I could help. I made a proposal that I didn't even want. Marina's mother-in-law has helped me feel very comfortable and happy.