How can Hyouma see and use Gennosuke's technique when he permits to do so?

Question

Hyouma is completely blind by birth. There is no doubt on this. But there is an unexplained connection between Hyouma and Gennosuke. With the order/granting/permitting of Gennosuke, he becomes able to

1. see.
2. use Gennosuke's ability to control other people's bodies.

What is the explanation of this behavior? What exactly is Hyouma's special ninja technique?

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It is used in only two scenes which are listed below. Note that, in the both times, Gennosuke was temporarily blind because of the poison of Hotarubi's snake. His blindness may have something to do with it.

Episode 11

Episode 17

Answer 1

Naturally, the answer contains spoilers.

Because Hyouma is actually the one who taught Gennosuke his eye technique. Gennosuke inherited the Dojutsu skill from his mother, and as his uncle, Hyouma also possesses the same Dojutsu skill. However, Hyouma's case is special as

1. In the anime,

   Hyouma's Dojutsu is constantly activated, forcing him to keep his eyes shut at all times to avoid killing the wrong person at the wrong time.

2. In the original novel and manga,

   [Hyouma] was born with light-sensitive eyes, [and therefore] is only able to open them at night or other low-light conditions.

Reference: Basilisk Wiki.