Senjuushi: Kijuushi-tachi no Happy Birthday! (The Thousand Musketeers: Noble Musketeers' Happy Birthday!)
Unaired episode titled "Kijuushi-tachi no Happy Birthday!" (Noble Musketeers' Happy Birthday!) that will tell a "heartwarming, hilarious slice-of-life story" about the noble musketeers holding a surprise birthday party for Master on a certain day after the events of episode 6.
[Source: Anime News Network]