Complete the indicated task to unlock the corresponding bonus. If any of the DLC has been installed, you can change character models earlier than by completing the game. To change the models of the male characters (Kaito, Yuto, Pops, Zenya, Sakaguchi and Soga), you must complete all four routes.

Bonus	How to unlock
"The Standard" Character motion accessory	Complete the game.
Akihabara NPC character models	Complete the game with each girl's route.
Anti-Gravity Primer motion accessory	Complete all five character routes.
Berserk Touko model	Complete the Rin Route.
Brainwashed Kati model	Complete the Shion Route.
Change character models	Complete the corresponding route for a characters; for males, complete all the heroine routes.
Change partner's underwear	Complete the game. You must be also be able to change that character's outfit.
Character affection hint option	Complete the game under the Casual or higher difficulty.
Character model size change	Complete the game under the Casual or higher difficulty.
Character Skin Tone Change	Complete the game under the Casual or higher difficulty.
Character Voice Change	Complete the game once under the Gamer difficulty.
I'll Try Higher Tomorrow motion accessory	Complete the game with at least 50% of all sub-missions finished.
Invisible Clothing mode	Complete all five character routes under the Casual or higher difficulty.
Kaito's model and shoes	Complete the Touko Route.
Kati's model, shoes and talisman	Complete the Touko Route.
Master's model and shoes	Complete the Touko Route.
Mind-controlled Kati model	Complete the Shion Route.
Nana's model, shoes and parka (hood down)	Complete the Sister and Nana Route sub-missions.
Ornery Touko model	Complete the Rin Route.
Pops' model and shoes	Complete the Touko Route.
Rin's model, shoes and memento	Complete the Rin Route.
Sakaguchi's model, glasses and shoes	Complete the Shion Route.
Shion Kasugai's model, shoes and amulet	Complete the Shion Route.
Shion's mask, lab coat and disconcerting rosary	Complete the Shion Route.
Shizuku Tokikaze's model, shoes and rune	Complete the Shizuku Route.
Souga's character model and shoes	Complete the game under the Casual or higher difficulty.
Touko Sagisaka's model, shoes and safeguard	Complete the Touko Route.
Transparent clothing mode	Complete all five character routes.
Try Again Tomorrow motion accessory	Complete the game with at least 50% of all Sub-Missions finished.
Walk With Your Head Down motion accessory	Complete the game with 100% of sub-missions finished.
Yuuto's model, glasses and shoes	Complete the Touko Route.
Zenya's character model and shoes	Complete the Rin or Shizuku Routes under the Casual or higher difficulty.