Secret life of my wife / Hidden essence

The main character of the hentai, Masato-kun, lives in a happy marriage with a modest and obedient Ichika-san. Although their marriage is already quite long, they still have bright feelings for each other as if the honeymoon never ended. But everything ends one day - one fine day Masato receives a strange envelope with the inscription "the truth about Ichiko" and inside is a disc with a very explicit documentary film of the corruption of a modest high school girl...