Obtained: After Chapter 3, you will receive a Topic from Tiki. Once you read it, head on over to Bloom Palace and speak with her.
Tiki is craving a donut so agree to purchase a honey-caramel-banana-chocolate donut (yummy!!!) and head on over to Hee Ho Mart. Select the option to “Buy Donuts” from the Salesclerk (regular one, not the masked one) to trigger a dialog scene. Of course it was sold out so begin your hunt for the high school girl. The girl waiting for the signal by the crosswalk east of Hee Ho Mart drops the hint that the culprit is a girl with headphones. Since no one fits that description on the streets, head to Cafe Seiren and go inside to find out that the girl who bought the donuts is Tiki=Waifu!! After the cutscene, you’ll send a Topic to Tiki letting her know that you got them then head to Tiki and speak with her to trigger a cutscene that will complete the job.