Dark Matter
Dark matter is an invisible substance that may exist in the universe. Although it cannot be directly observed for now, there is extensive evidence that it exists in the universe, just like Shen Yuxiu's love for Song Ning. Although he dares not admit it, every glance and every action he takes says, "Shen Yuxiu loves Song Ning." Song Ning tried her best in the process of loving Shen Yuxiu. She knew that they could not continue like this forever, and there would be others by his side one day. So she was always testing him, intentionally or unintentionally revealing her possessiveness; until one night after she got into university, she couldn't control herself again and crossed the line between them...
At the same time, she received a letter, the contents of which stirred up a forgotten past. A cool and tsundere sister with a tsundere exterior who is awkward on the inside x A gentle, introverted, and slightly yandere brother (pseudo-incest).
A story of mutual salvation, daily life, written with interspersed flashbacks. The writing may not be good, the plot is melodramatic, with a HE ending. It's clean in the early stages and becomes explicit later. 1v1, H, modern campus.