This special takes place just before and during the final episode of the main series first season. Basically it's just to explain how Motochika and Motonari put aside their differences to take down the Oda once and for all. It feels a little rushed, like a side story they planned on fleshing out more but didn't have time for so they just threw it all into a single episode and included it as a DVD bonus. It makes sense that they cut it out, as it probably would have distracted too much from the main narrative of Yukimura and Masamune they were trying to focuson.

It felt like Motonari got too much of a pass for clearly reprehensible behavior, and the single friendship speech from Keiji was a bit too much talk-no-jutsu for my liking. Overall I feel like it's a special that'd be good for introducing who these characters are if you didn't know them already, but skipping it wouldn't detract much from your experience watching the anime series. 7/10