When he suffered a massive defeat in his first faceoff against Moro, Son Goku decided to undergo intense training with Merus at the Hyperbolic Time Chamber. Merus, who was initially introduced as the strongest member of the Galactic Patrol, turned out to be a trainee angel who is very familiar with Son Goku's special technique, Ultra Instinct. In the latest chapter of Dragon Ball Super manga, Son Goku showed the result of his training.
Like the Gods of Destruction and Angels, Son Goku's Ki can't be easily sensed by a mortal and after activating Ultra Instinct, his speed dramatically improved. Also, unlike when he first unleashed Ultra Instinct in the Tournament of Power, Son Goku can now use it whenever he likes. Dragon Ball Super Chapter 59 featured Son Goku easily dodging every attack of Moro and hitting him with lightning speed.
Moro tried to immobilize Son Goku by putting seals in his hands and feet. However, Son Goku only took a few seconds to remove the seals and return to action. Piccolo and Son Gohan were both amazed by the tremendous improvements made by Son Goku and confidently said that he could beat Moro. Son Gohan also told his father not to worry about going all-out since they have already gathered all the Dragon Balls if ever Earth will be heavily damaged during his fight against Moro.However, despite overwhelming him at the start of their battle, Dragon Ball Super Chapter 59 revealed that Moro still hasn't used his full power. Also, though he could already activate Ultra Instinct at his own will, Son Goku could only use it in a short period of time. While having a conversation at Beerus' planet, Whis praised Merus for the result of his training with Son Goku.
Unfortunately, when Whis asked if Son Goku has already learned the Mastered Ultra Instinct, Merus gave a negative response. He revealed that Son Goku only managed to achieve the Ultra Instinct Sign level. Whis explained that Ultra Instinct Sign only serves as a gateway to Ultra Instinct. If it isn't stable, maintaining that instability consumes an enormous amount of stamina. Merus said that the outcome of Son Goku's battle against Moro depends on his ability to manage the energy drain while keeping Ultra Instinct Sign as long as possible.
The final scenes of Dragon Ball Super Chapter 59 featured Moro noticing the flaws in Son Goku's technique, saying that he just needs to buy time to win the battle. However, it seems that Son Goku no longer cares about the stamina balancing act Merus suggested and is already planning to use his full power to beat Moro.