Board Thread:Boruto Discussions/@comment-25319479-20160502145551/@comment-734582-20160506075100

Makimaki11 wrote: What is Senjutsu? Sage Techniques. And since "sage" in this context refers to people who absorb nature energy, it's simply the use of nature energy in techniques.

As to tattoos, they can be used as recipes for techniques or as seals. So it could be anything.

Regarding Boruto's eye, if i remember correctly Byakugan is always activated by saying "byakugan!" plus veins and everything. I still put my money on it being a non-activated, transplanted Byakugan.