The Shin Kogakugan (真光学眼, True Optical Eye), is the advanced form of the Kogakugan. So far the only member to activate this, is Kibishī Masakari. It seems that in order to activate this stage of the dojutsu, the user must have the Kogakugan active at all times. Doing this will develop it at a faster rate than deactivating and activating it constantly. However, the Shin Kogakugan can only be activated for a short period of time because when in use, it begins to fatigue your sight. This causes strain on the optic nerves, disabling your vision but not completely going blind, so now the user can't use the dojutsu for 72 hours. This will allow the optic nerves to heal and respond back to normal.