Tamashii Insert

Following the death of his mother and his father's remarriage, an ordinary young man named Naoto finds himself living with two new women: his stepmother Sachiko and his stepsister Yui. Concerned by Yui's emotional distance, he discovers a strange application on his phone that claims to help its user understand another person. When he uses it on Yui, he unexpectedly finds his consciousness transferred into her body. Confused by this possession, Naoto sees Yui's reflection in her room's mirror. Overwhelmed by the sudden urges arising from his sister's form, he proceeds to explore her body. This leads to acts of self-stimulation focused on her breasts and nipples, indulging in the novel physical sensations available to him.