WARNING: The following contains spoilers for Boruto: Naruto Next Generations Chapter #53, “That's Reality,” by Masashi Kishimoto, Mikio Ikemoto, Ukyo Kocachi, Mari Morimoto and Snir Aharon, now available in English from Viz Media.
When Momoshiki appeared with Kinshiki in Boruto: Naruto the Movie, it seemed as if they were the only Ōtsutsuki clan members left, trying to take the planet after Kaguya failed in the Naruto series. However, even after they were beaten, Momoshiki lived on by placing a Karma mark to be reincarnated in Boruto, which is now being expanded on in the manga and anime. However, following recent revelations made by Momoshiki concerning the rise of another clansman in Isshiki, there's a plot hole that has arisen with respect to the alien species and their mission on Earth.
In the Boruto solo film, and even when the fight was extended in the anime, Momoshiki made it clear he only knew about Kaguya. Her failure was their window of opportunity and as a result, he and Kinshiki saw the planet ripe for the taking. However, the manga would later reveal Kaguya came with a partner in Isshiki and she eventually betrayed him. A wounded Isshiki would then secretly take over Jigen's body to be reborn, waiting it out for centuries until Kaguya fell and the Kara terrorist cell was able to help him drain the planet.
The problem is, Momoshiki mentions he knew about Isshiki, yet that was never the case in the past. If so, he'd have known Isshiki was alive in Jigen's body, and rather than just going after Naruto and Sasuke, he and Kinshiki would have had to hunt Jigen down because Isshiki would have meant resistance. After all, they were all competing to see who'd feed on the planet's essence, consuming the chakra of all humanity.
It does seem like plot convenience here because again, there's no reason for Momoshiki, upon possessing Boruto, to taunt the heroes about wanting to see if they could beat Isshiki, when back then he supposedly didn't even know his brethren existed. This memory gap on Momoshiki's part is going to be very hard to explain, as he hates and maybe even fears Isshiki, so there's no reason to forget him. Also, the retcon about clan members coming in pairs is new, but seeing as Momoshiki came with Isshiki, he should have known all along there was a second person who came with Kaguya.
And to double down on the plot hole, while Jigen was lying in wait all these years, storing up Isshiki inside him, we have no clue why he didn't emerge to fight Kaguya and also, to take Momoshiki and Kinshiki down himself. It's just so weird for the series to put them all in this rat race, yet they never know where each other are despite being dispatched to designated zones. The franchise has muddled this history so much. Hopefully we learn why Momoshiki stayed away from Isshiki's path and a rebirth vessel in Kawaki, and Isshiki steered clear of his. They clearly knew about each other and were enemies gunning for the same prize, so it's an odd choice that they never really spoke about the clan problems until now.
