OVA episodes bundled in limited edition volumes of the manga. 
 
The first is Ban no Bangai-hen, which shows a part of the past of Ban. 
 
The second is a collection of 9 short stories. Those are: 
“Muda na Mono Nante Nani Hitotsu” (Nothing is wasted) 
“Oshiete Danchō!!” (Teach Me Captain!) 
“Zanpan Shori Kishidan Danchou no Jikenbo” (Case of the Captain of the Leftover Disposal Knights) 
“Diane to Ban” (Diane and Ban) 
“Naku na, Tomo yo” (Don't cry, my friend) 
“Gilthunder no Shinjitsu” (Gilthunder's Truth) 
“Kekka Yokereba Subete Yoshi” (If the Results are Good, Everything's OK) 
“Uso to Makoto” (Lies and Truth) • “Aibou” (Partner)
 
(Source: Anime News Network)