In episode 34 of the series, Boruto and his ninja academy friends go on a fishing trip to catch the "Eternal Carp," a fish that was supposedly so tasty they would remember eating it forever. At first when they failed to catch any of the carp, as a recent rainstorm had changed the current of the river, Boruto decided to keep trying to catch the elusive fish far into the evening.
After a heart to heart with his classmates Sarada and Sumire, Boruto's fishing line finally gets a bite. The carp ended up being so huge, Boruto needed support from the rest of his classmates in order to successfully reel it in.
Sarada grabs the line to assist him, Metal Lee cuts off the fish's escape route with kunai, Shikadai uses his shadow jutsu to keep Boruto and Sarada in place, Iwabe forms a rock wall to keep them from falling off the cliff, and Sumire summons the cutest character in the series so far: a pocket-sized version of her formerly ferocious summoning beast, Nue.
Back during the "Academy arc" a series of incidents were caused by shadowy auras Boruto and his friends deemed "Ghosts." The origin of these ghosts were eventually revealed to be Sumire, who had been on a mission from her father to destroy the Hidden Leaf Village with a destructive beast that fed off of other's chakra.
But after Boruto was able to talk Sumire after blowing up her summoned beast and taking herself out along with it, Nue was revealed to be a beast who highly regarded Sumire. Fans have yet to see Nue since its last appearance in episode 14, so this new form was surely was welcome surprise. Nue is sure to be a lot more popular in its pint-sized state.
For those unfamiliar with Naruto, it has quite a storied history. Originally created by Masashi Kishimoto, the series ran in Shueisha's Weekly Shonen Jump for 700 chapters. The story follows Naruto, a young ninja with a sealed demon within him taht wishes to become the leader of his home village. The sequel, Boruto: Naruto Next Generations is set several years after the events of the original Naruto story and featuring the children of many of its key characters such as Naruto and Hinata.