File:That Time I Got Reincarnated as Kosaku Shima.jpg

Summary
What if the protagonist of That Time I Got Reincarnated as a Slime did not, in fact, get reincarnated as a slime? What if he became the protagonist of a different manga instead?

That's the premise of Kenshi Hirokane's latest new installment of the Kosaku Shima series. The eponymous protagonist has been climbing the corporate ladder since 1983. With every change in job title the main character receives, the manga title also changes. The manga began under the name Kachō Shima Kōsaku (Section Chief Kōsaku Shima). Sequels include Division Chief Kosaku Shima, Managing Director Kosaku Shima, Executive Managing Director Kosaku Shima, Senmu Shima Kōsaku, President Kosaku Shima, and Chairman Kosaku Shima. He has now become such a successful businessman that surely other people would want to be him, and that's exactly what happens.

Instead of transporting to a fantasy world, the 37-year-old protagonist of That Time I Got Reincarnated as a Slime will awaken as a 37-year-old Kosaku Shima in the year 1984. Titled That Time I Got Reincarnated as Kosaku Shima (Tensei Shitara Shima Kōsaku Datta Ken or Regarding Reincarnated to Shima Kosaku), this manga will be a collaboration between Kenshi Hirokane, the That Time I Got Reincarnated as a Slime novel author Fuse, and manga adaptation artist Taiki Kawakami. The story is set in a "parallel universe" - you can think of it as one of many possibilities for That Time I Got Reincarnated as a Slime. The manga will begin serialization in Kodansha's Evening seinen magazine from March 12.

And what has happened to the real personality of Kosaku Shima while the Slime protagonist is in his body, you may ask? A spinoff manga published in Comic Zero Sum will focus on Shima's exploits as a medieval knight after he gets reincarnated into a fantasy world. That series is slated to begin on March 28, so readers can enjoy the tales of two Kosaku Shimas in different worlds.

Source: https://www.animenewsnetwork.com/interest/2019-02-25/new-chairman-kosaku-shima-manga-is-a-that-time-i-got-reincarnated-as-a-slime-crossover/.143847