Guin Saga

Both are about masked man with no memories being cought in battles and politics. 

Both are about a war and both main characters are great strategists. 

The main character in Utawarerumono wears a mask he can not take off and has lost all his memories 

As others have stated, Utawarerumono is clearly based upon the original Guin Saga novels. Both feature a mysterious masked man with no memories rescued by and protecting two siblings. Both series are about fighting for freedom against an oppressing and more advanced kingdom. Even many of the side characters are similar. The only real difference is that Utawarerumono is much more 'anime-like', whereas Guin Saga feels much more Westernized.  

Both Epic Fantasy tales. Guin Saga has a western approach to fantasy while Juuni Kokuki is more focused on far east fantasy. And both are very good and incomplete. 

Epic fantasy set on a large scale involving numerous kingdoms and several characters. Politics, wars, palace intrigues and sorcery. Juuni Kokuki shows Chinese influences while Guin Saga leans more towards Persian & western literature and historical epics  

12 Kingdoms is a series that literally puts you in the heart of a story, an adventure that will appeal to any fan of Asian culture, Chinese or Japanese. This adaptation is beautiful and well done. Nothing was left out. The sets are processed, giving the impression of having actually entered this world. Different clothes are separate from those of the people and those silk. Nothing by the appearance of clothing, we can discover the status of the character. Given the fact that the 12 Kingdoms takes place in a world inspired by Asian Middle Ages, we find the codes of the time. Like the novel, storytelling can be viewed separately although for some there is a link driver. These stories lead clothing mythology, politics, intrigue and adventure. Finally, the soundtrack is wonderful. The use of traditional instruments (probably Japanese), is an effective gateway to immerse ourselves in this universe.  read more 

Political unrest in a fantasy world, captivating characters and a more adult feel to the anime. Also, both end before the story has been completed. Bah. 

Miura Kentaro said that Guin Saga had a large influence on him whilst he was working on Berserk. Both mains are similar in many ways. Both mains have large builds; Both inhumanly strong; Have travel companions; Have mysterious backgrounds; And also constantly fight. Guin is more of a calm strategic type person whilst Guts is a reckless person who won't hesitate to kill. Only differences are that Guin has a leapord head and does not weild a sword which is the same length as his height. Unfortunatly, Guin Saga was never finished and probably never will be finished due to the passing away of the author. 

In short: -Swords -Nation wars -Hack and slash -Head character having a huge sword -Silent head character -Supporting side characters -Plotting -Adventure -Medieval -Magic 

They both revolve around the theme of heirs reclaiming their country. In terms of appearance, Remus and Arslan are also very similar. The only difference is that Guin Saga features twin heirs and is slightly more fantasy themed. 

They are similar because both are about siblings that go to war with a more powerful force, but it's mostly because you get the same kind of atmosphere from both of these shows  

The source materials for both are long novels series, yet both are also similar in the sense that their anime counterparts are incomplete. However, each of them definitely capture the essence of their expansive fictional worlds modelled after historical periods and places, and the grand scale of the storylines. The intricacy of the plot, albeit unexplored due to the lack of completion, and the diverse cast of characters also carry a similar vibe. Political intrigue and different 'sects' of characters are prevalent in both. And they contain fantastical elements, though more so in Guin Saga than Arslan Senki. And both series have rather melodious ending themes. 

both stories are about twins who get taken out of their world and meet an array of interesting characters along the way. both series also seem to carry out the theme of survival of the fittest and both have similar art styles. 

The character "Mercenary" Is very similar to the main character in Guin Saga.