At one point in the manga adaptation for Kingdom Hearts II, Sora abandons a battle in the Land of Dragons to search for Riku after receiving a Paopu Fruit via Shang from him, forcing his allies to go on without him.
Lieutenant Yamamoto of Irresponsible Captain Tylor meets up with the rest of the crew, attempting to rescue Tylor from a firing squad but unable to find him in his cell in order to tell them where the execution would be carried out.
Later however, just when it seems he's gotten himself into a hopeless situation, Ninth comes flying in to save the day.
In Future Diary, the reformed Minene parts ways with Yukki, telling him that he has to solve his own problems from then on.
Somewhat unusually, a whole chapter explains exactly why, and the trope is played less for the reveal that he comes back than to show character growth.
Cowardly Sidekick Pop from Dragon Quest: The Adventure of Dai leaves Dai and Maam when they go fight the big bad Crocodin, then shows up in the nick of time to help when they're in trouble.
Then, just as Cell was on the verge of overwhelming Gohan, Vegeta attacked Cell, catching him by surprise and distracting him for a moment, during which time Gohan upped his power and overwhelmed the distracted Cell. In the manga, when Cell and Gohan entered their Beam-O-War, everyone looked on helplessly instead of trying to attack Cell.
Which is different from how it went in the manga.
He fires a massive energy blast at Cell which distracts him, allowing Gohan to turn the tide and save the day. Just as all hope appears to have been lost, Vegeta (who was previously too busy angsting about not being able to do anything) joins the fray. all his friends are helping him out but to no avail.
In Dragon Ball Z, Cell is on the verge of overwhelming Gohan and destroying the Earth.
True, this was the Lighter and Softer arc, as Death Note goes, but his mad undercover skills and subsequent cavalry charge are no less awesome for that.
Ken Wakashimazu pulls that in Captain Tsubasa World Youth Cup, after the conflict with him and coach Mikami boils up to its limits since Ken feels he's The Unfavorite of the team, no matter how hard he trains.