You have to get all the virus chips. Here is where to go to get them:
Mettaur: ACDC 1 past the skull door.
Bunny: Job 19.
Spikey: Demon Comp directly north of where you enter.
Swordy: Undernet 1 in the blue section's second dead-end.
Jelly: Beach 2 to the left of the Undernet entrance.
Mushy: Sci Lab 2 to the left of the Sci Lab Square entrance, in the tiny square.
Momogra: Zoo Comp 4 where you battled Beastman.
Killereye: Principal's PC 1 near the entrance to Principals PC 2.
Scuttlest: Note: There are two parts to the Scuttlest family. The first is
located in Secret Net 1, directly left of where you enter. The second is located in Secret
Net 3, all the way north of the press pathway, to a dead-end
The exception is the second part of the Scuttlest family, as you cannot get them until you open the Door of Love.