Special stickers will appear in certain stores during the week a character is introduced. Typically, they're purchased using Scarletite pins, received primarily through story events, and for one sticker per character, other pins like Rare Metals and Tektite. Each sticker grants an extra level of fusion.
Shiki's stickers are in Go-Go Gear 104 for 2 Scarletite, and Go-Go Gear Molco for 2 Scarletite and 2 Rare Metal. Joshua's stickers are in Luxury Fashions, Shibu Dept. Store for 2 Scarletite, and Import Stylings, Shibukyu Main Store for 2 Scarletite, 3 Rare Metal and 1 Tektite. Beat's stickers are in B-Style Threads 104 for 2 Scarletite, and in Wild Boar, Udagawa Back Streets for 2 Scarletite, 3 Rare Metal and 1 Tektite.