Boruto Episode 141: Boruto & Mitsuki being prisoned at the Hazuki Castle administrated by the Hidden Grass Village. This, in fact, is their mission assigned by Naruto, the 7th Hokage to protect Kokuri. Not only that, but the leader of the Hazuki Castle is helping the leaf village to investigate.
The entire plan is made by Naruto, & Shikamaru Nara along with the Leaf police. The reason they had to take this action was due to Hidden Grass elders who denied protecting Kokuri & making it their internal affair.
Not only that, but Naruto also assigns Sarada as a reporter so that she can eye on Boruto & Mitsuki.
Meanwhile, Boruto & Mitsuki find out that the 2nd Man’s name is Tsukiyo who is in solitary after getting in a fight with Kokuri. Later we find that the one who sent the letter was Kokuri. By the time, Naruto exits the hospital, someone attacks Kokuri.
This concludes that someone who is against Kokuri is from the Hazuki Castle. We will get to know about this on Boruto Episode 141.
Watch Boruto Episode 140
You can now watch Boruto Epiosde 140 with Boruto Wiki. The below URL is iframed from Crunchyroll, which is the legal streaming platform to watch Boruto Episode 140.