A rare situation where a father brings home a new young wife close in age to his son. The new wife is a glamorous, big-breasted beauty who tries to build a closer bond with her stepson by spending time together under the kotatsu. As they sit close under the heated table, their bodies begin to touch. Gradually growing more intimate, feelings start to develop between them, leading to rising desire. It is the stepmother who makes the first move—secretly stimulating her stepson's hardened penis behind her husband's back, giving birth to a forbidden, passionate relationship.