Tesuto, thank you for the weekly translations up until this point. I hope your work-related matters are smoothed over soon.
As for stuff within the chapter- Another game series is now crossing over! So this wouldn't be DLC characters, unless it was by the same company. But, I will say- it does have the flair of a 37 year old game from the 8bit/16bit era. I mean, a robot warrior and a demon princess?
I think the author left off ten years though- 27 years would be about year 2000, when Final Fantasy 9, Majora's Mask, Grandia II, Paper Mario, and pokemon g/s/c were released. Unless the pictures on the guide book are simply more stylized for the artists sake, the art points towards a even older series.
Though, I guess it could've been like Dragon Quest 7, who came out with a older style of graphics. Since this is called "Oedo Tactics" I would guess that this is a tactical game, or perhaps a real-time action game. Certainly not a otome/dating/life simulation game.