The Forbidden Jutsu of Death

Boruto and the team finally catch up to the real thieves, two ninja brothers from the Land of Kasumi. Yuga uses a Forbidden Jutsu to summon a monster, and seals it and the team inside a strong barrier. Naruto insists on defeating it and getting out of the barrier. But Mugino argues that unnecessary fighting should be avoided since they don't know how to counter this special jutsu.