Interesting to know and learn about Jijang-Jeon because of praying for the people in hell. In real Christianity we do not pray for the dead, when a person dies his spirit goes to God already that gave it and soon it will be judged if it will go to heaven or hell. It is for the living that we should pray so that he will get saved from hell.
I don't know what you mean by 'real' Christianity seeing that for 1600 years before the rise of Protestantism there was a long tradition of praying for the dead in the church. The sola scriptura movement with its various emphases is a comparatively later phenomenon. Here's a post from another steemian who used to share your view and has now changed - https://steemit.com/life/@creatr/do-you-pray-for-the-dead-ruminations-on-god-s-sovereignty-over-time. Some things are not always so cut and dried, my friend.