WARNING: The following contains spoilers for Boruto: Naruto Next Generations Episode 182, "Ao," now streaming on Crunchyroll.
In the Boruto anime so far, Mitsuki's devotion to the title character has been unquestionable. It's comparable to how Shikamaru was with Naruto in their teens, and it continued to redeem Orochimaru for letting his 'son' choose his own path.
However, in Episode 182, Mitsuki just changed his entire dynamic with Team 7, chiding Boruto for his brattish ways, and honestly, it's for the better.
Naruto orders Boruto on a C-Rank mission to head to Ryutan with Katasuke so the science team there can improve on what Konoha created with his prosthetic arm. However, Boruto's still annoyed Naruto used it in their sparring session, considering it cheating. In addition to that nuisance, he doesn't like how science tools are seen as progress. Not even Sasuke can convince the stubborn teen otherwise, causing him to storm out and go for ramen as he doesn't feel like the adults are taking him seriously.
But as he sulks in the booth, Mitsuki and Sarada visit, with the Uchiha girl making it clear she's going to accompany Katasuke as all jobs are important to her. Mitsuki, with his cheerful disposition, then reams Boruto after she departs by telling him he needs to grow up. He admits in the past once Boruto didn't go on a mission, he wouldn't either. It's because he has so much faith in his buddy, but this time, he's going without him.
Mitsuki admits that mode of thinking is done -- he wants to be his own warrior. He asks Boruto to consider his family, friends and the entire village, because every mission, whether it's Kara or helping old folks, helps contribute to their safety. It's a more mature Mitsuki and a stunned Boruto confesses despite his tantrum he was always taking the job, which Mitsuki admits he knew was always going to be the case. Still, he had to chide Boruto, offer up this harsh lesson and let him know their partnership was evolving in any case.
This comes right after Mitsuki got patched up to help him defeat Deepa and Victor, with even Orochimaru stunned by how desperate and loyal he was to save Boruto. Log noticed it too and it seems Mitsuki has returned, not just with a stronger body but mind too. He doesn't have time for Boruto's childish ways and ego anymore because, after the Deepa fight, they could have all been killed.
It's why he's going to follow his own heart, as he knows that rash kid might get them murdered. By adopting this philosophy, he can take better care of his teammates and serve the village as the old Orochimaru did as a legendary Sannin.