WARNING: The following contains spoilers for Boruto: Naruto Next Generations Episode 222, "The Night Before The Final Round," now streaming on Crunchyroll.
With the Chūnin Exam in full swing once again, Konoha's younger generation of shinobi must prove to Naruto and co. they're fit to graduate and become the new protectors of the village. Most are already running missions as genin, but this is the true litmus test to show the council who'll be the next elite bunch of ninja. Unfortunately, as it kicks off in the Boruto anime, some bad news has been sent that confirms the Hidden Leaf will be losing one of its biggest prodigies.
This is none other than Tsubaki Kurogane, the young samurai who came over to the Land of Fire from another country, the Land of Iron. When Sumire left Team 15 to join the science team, Naruto asked Mifune to send someone over as he wanted to bridge the gap in their relations.
The leader chose Tsubaki, one of his best samurai, a decision Naruto trusted as Mifune was a key player in helping him during the Kaguya War, fighting off Madara's soldiers and Hanzo. But it took a while for her to get acclimated as she was cold, and far more disciplined than Konoha's crew. This is due to her people being neutral, ergo why Mifune advised all the Kage in the past, which led to Tsubaki being mature for her age and a tad condescending.
However, as time rolled on, Tsubaki acclimated to Wasabi and Namida under Hanabi's tutelage. She learned that as much as she wanted to use her sword for peace, diplomacy and loyalty matter too. Eventually she scrubbed her ambitions of being a one-woman army, working more with Boruto and his friends. This growth throughly impressed Naruto and his seniors, as Tsubaki used her warmth and compassion to create chakra tornadoes from her blade, which -- along with her agility -- felt like a young female Sasuke at times.
Sadly, as much as Tsubaki has progressed and taught Boruto's peers about being more serious in the field, Episode 222 reveals her time is at an end. Just as she preps for her final test, a letter comes over that confirms the Land of Iron wants her back to fill a leadership position.
Mifune trusts her, knows her development has exceeded expectations and with Naruto's glowing appraisal, they think she's ready to help them at the highest level. Tsubaki was scared to tell her team, but the girls make it clear they're proud of her achievements.
It's been pretty remarkable to see Tsubaki evolve from an outsider into someone so motivating to the others, and as Boruto put it once, she's a wunderkind that feels like she's been with them their whole lives. Her journey went from a student-exchange program to being part of the Konoha family, and with all this love in the air, Tsubaki wants to leave a big mark in Boruto by graduating before heading back home.
