Shokukōgan

The is a dōjutsu kekkei genkai of the Karasuji and Ōtsutsuki Clans, inherited by an unknown Ōtsutsuki clan member. Despite not being one of the three great dōjutsu, it has been widely renowned in the Shinobi World.

Overview
This dōjutsu is usually manifested as an eye with large irises with vibrant colors, and its edges in a squiggly pattern. When in use, the iris colors change along the spectrum. Like the Byakugan, the Shokukōgan is available at birth, but it takes time before the kekkei genkai starts to improve.

It is highly coveted, and is sought after almost as much as the Byakugan. Unlike the Byakugan, the Shokukōgan was created with an internal "seal", which prevents it from ever being stolen to one not of Ōtsutsuki or Karasuji descent.

Abilities
The Shokukōgan links the olfactory and visual systems. The kekkei genkai allows the wielder to smell a certain scent, and have their eyes color code it, allowing the user to track down anything that has the specific scent through color. As such, it is widely used for search/tracking missions.

The color coding is only temporary, canceling after stopping the use of the dōjutsu or through other means like fainting or after losing too much chakra. This means the user has to constantly use the dōjutsu, while consuming chakra, if they are involved in a pursuit. Additionally, the scent could be scattered by wind, potentially confusing one with the Shokukōgan.