Kidnapping

An alternative to murder, Yandere-chan can instead kidnap her rival. To do this, she must have a good reputation, a syringe, a tranquilizer, a locked room to hide the body, and a case to store the body.

Steps
First, Yandere-chan must have a good reputation, in order to convince her rival to follow her into a locked room.

She must also possess a syringe with tranquilizer inside it - both of which can be found in the Nurse's Office. However, the Nurse is always on guard, and you won't be able to obtain these easily. The exact details of the process are not available, as they have not been implemented yet. For now, they're simply lying on the desk inside.

She must also have a case to store the body in the locked room, which can be obtained from a favor from Info-chan.

If you have all of these, wait until school is over, then ask your rival for a favor. Ask them to follow you. Lead them to the locked room and close the door, attacking them with the syringe before they can figure out what's going on. Dump the body into the container, and then exit and close the door to the room again. Leave the school - you will come back during the night to pick up the victim.

The next morning, if you go down to your basement, she will be there, tied up and staring at the ground. Congratulations - you have successfully kidnapped your rival!