Besides the Treasure Box, D also released a 10th anniversary single, called Bon Voyage!. This single was only available at their 10th Anniversary Special Premium Live "Bon Voyage!" concert at Shibuya Koukaidou on April 12 2013. Thankfully, there were a few people who put them up for auction after the concert.
Speaking of a single only being available at a concert, I also got Mayutsuki no hitsugi (繭月の棺). This single was for sale at three concerts in November 2004 in Tokyo, Nagoya and Osaka. There is no difference in songs between the three. The only difference is the cover, and the city name at the end of the title. I got my hands on the first version, the Tokyo one, called Mayutsuki no hitsugi ～Tokyo uka～ (繭月の棺 ～東京羽化～).
After these two orders, eight more to go.