Mother-in-law got pregnant while traveling with the whole family

Ken and his wife have been married for a while, but neither of them has any children yet. Because they wanted to see their grandchild soon, his wife's parents asked him to abstain from all lewd things, including masturbation. So that when the whole family goes on a hot spring trip next month, he will be at his best. After a month of suffering, Ken was about to reach his limit.

But when the family arrived, his wife kept finding reasons to refuse. While walking around to relieve his arousal, Ken accidentally witnessed his mother-in-law taking a bath. And while losing control, he did something unforgivable...