It looks like the ruling party is intending to continue the trend of putting ex-ROK Presidents in jail:

Following former national security adviser Suh Hoon’s arrest on Saturday for allegedly covering up North Korea’s killing of a South Korean official in the West Sea, clashes between ruling and opposition parties are intensifying, with eyes on whether the investigation will target former President Moon Jae-in.
The prosecution issued an arrest warrant Saturday at around 4:55 a.m. against former national security adviser and spy agency chief Suh after more than 10 hours of questioning, citing the “risk of Suh destroying evidence.” Suh was the first presidential aide of Moon to be arrested among those accused of mishandling of the death of South Korean Ministry of Oceans and Fisheries official Lee Dae-jun in September 2020.
The ruling party and an attorney representing the deceased official’s brother Lee Rae-jin are ramping up calls for justice over the former Moon administration’s labeling of Lee Dae-jun as a South Korean defector to North Korea. This had effectively relieved Seoul of its duty to protect Lee and acquitted Pyeongyang of its summary execution. Meanwhile, evidence that Lee was a defector remains under question.
The ruling People Power Party interim chief Chung Jin-suk said in a statement Saturday on social media that Moon’s statement last Thursday indicated that Moon should be held accountable for the border killing case.
Korea Herald
You can read more at the link, but if the ruling party moves forward with trying to jail former President Moon it will pretty much be a guarantee that current President Yoon will be tried for something once the Korean left regains power.
With that all said it would be interesting to find out who in the Moon administration pushed to label the fishery official as a defector in order to not impact their North Korean appeasement strategy.