The Synthesis Wizard - Chapter 13 - : Wizards Seek Truth, Not Immortality

Ever since He Mulan, a 28 year old forensic investigator, transmigrated into the post-army civilian Hua Mulan’s body, she’s been under a lot of pressure. Unlike the folktale ending, there are no flowers or applause to be found here. After leaving the army and returning to her hometown, word by the countryside has painted the now 32 year old Hua Mulan as a homicidal maniac, an old hag, and a freak of nature, among other nasty things. Between piecing together Hua Mulan’s scattered memories, grappling with her fellow villagers’ prejudice against her, and fending off Mrs Hua’s attempts to match make her, He Mulan has her hands full. All He Mulan wants to do is protect Hua Mulan’s body till her soul comes back, but fate has other plans…

- Description from Novelupdates

After living in a desolate land, where there wasn’t even a single blade of grass and hunger was an everyday reality, Min Sung finally returns to Earth: his home.

I became the childhood friend of the protagonist in a novel. The childhood friend who died from taking drugs.