Wrestle Kingdom 13 was a huge event, which saw all champions losing their titles, and that included Kota Ibushi losing his title to Will Ospreay.
After the brutal and physical match, Kota was carried out on a stretcher. According to Dave Meltzer on Wrestling Observer Online, although Ibushi had legitimately suffered a concussion, a stretcher was always going to be in play once the match ended.
The thing of the idea at the Tokyo Dome with Kota Ibushi was a work. The idea of the work, but Kota Ibushi is injured, but the stretcher job, he was not injured where he needed to go out on a stretcher. That was always planned.”
The “flash knock out” on Ibushi when Ospreay hit him in the back of the head was according to plan, but not the concussion that Ibushi suffered. A stray kick in the corner was what caused the injury. The stretcher was planned in order to write off Ibushi for “a few months.”