Even More of Roku's Kit

Name: Kikaigan
Type: Equipment
Canon/Custom: Custom
Rank: S
Durability: Same as user's stat, whatever it may be at any given time.
Material: Biochemical compounds and bio-mechanical technology
Equipment Ability: Kikaigan is a pair of mechanically engineered eyes for ninja.  They must be transplanted into their eye sockets and replace their current eyes, which is assumed to have been done upon purchase by the person it is purchased from, though the user can have a topic to do so if they wish.
[list]
[*]The user can spend 5 CP per turn to be capable of seeing 360 degrees, similarly to the Byakugan but it cannot see through walls and does not enhance the user's vision range, giving them +50 perception.
[*]The user can pay an additional 5 CP per turn as the Kikaigan stimulates their other senses, giving them another +50 to perception.
[*]When one has these eyes, because of the difference in their required biology, they cannot be subjected to Genjutsu that trigger on eyesight, and their eyesight cannot be fooled by Genjutsu.
Cost: 10k
Requirements: Just 1 set exists.

I'd like some clarity on how exactly the second skill is meant to work. What other senses are this set of eyes enhancing specifically? Because enhancing hearing or smell could have its own downsides in specific situations, so I'd like this to be more clear.

Also, I don't understand why only one set exists if these things are being specifically purchased by a merchant in-universe. Considering another perception-boosting synthetic eye already exists, it seems like this would be something that wouldn't have such a hard limit on it. Especially since, as a non-limited, this would be hard for new members to keep track of since people could just assume nobody's actually bought it yet.