The good items are:

Second opponent: Nanbankusoku. If you get four, you can combine them into Ultimate Western Armor, an armor that gives gives +20% defense and +20% troops

Third opponent: Eboshi of Matsutaira. It gives +15% defense, with an extra +10% defense for an archer. That's +25% defense for archers.

Fourth opponent: possibly Seiryuu Armor. The Japanese wiki as viewed through Google Translate says "When the defense power is a multiple of 5, the damage reduced by 40%".

Seventh opponent: probably Seiryuu Armor again, and maybe Sparrow Tail-shaped Helmet. From the Japanese wiki, the latter is "Arriving at the beginning of the turn, recovering the force of military force x 10, increasing defense power of armed power x 10". From comments, it sounds like if you've got appropriate stats, that could be about +1800 defense and +1800 troops recovery per turn. Google Translate is wildly imperfect, of course.

I don't see any accessories in the event, and I'm not impressed with any of the weapons. Lots of good armors, though.