Your mission is for you to go to the Soul Society and seek out one, Eighth Seat; Tenth Division: Tsukiro Ashimitsu. Once you have found him -- Kill him.
*smirks* Take heed though, he has been spending much time with the Captain of the Thirteenth Division Juushiro Ukitake. I am sure the ailing Captain Ukitake is a match for you. However, if the chance presents itself, you may kill him as well. I expect a full report when you return.