Thorfinn is son to one of the Viking's greatest warriors, but when his father is killed in battle by the mercenary leader Askeladd, he swears his intent to have revenge. Thorfinn joins Askeladd's group in order to challenge him to a duel, and ends up caught in the middle of a war for the crown of England.

https://www.animenewsnetwork.com/enc...e.php?id=20778

Vinland Saga is my most anticipated series this season, based on a manga from the same mangaka of Planetes. Looks like it's well animated, so have high expectations for it.