Akatsuki no Yona OVA

People who do not age, who do not die. And yet, everyone around them does. This premise is explored in the Yona OVA (hot springs episode notwithstanding) and SayoAsa, where immortal beings form an intimate relationship with a normal, mortal person. The way in which it is handled in both works are a bit different, but they invoke a similar flavor of bittersweetness. 

Sousou no Frieren also has a main character who has a much longer lifespan and therefore must leave her former companions behind. But she joruneys ahead, making new friends and helping people. It feels a lot slower pace (although it really isn't imo) which might be a refreshing contrast to a fast-paced, action-packed story. 

Both are unaired episodes from TV anime shows that were released in 2014 and are about cute, shortie, redhaired girls who are surrended by a group of bishonen with funny personalities, taking each one a typical fan service episode theme(one the beach theme, and the other the bath theme) as plot. Also, we hope a second season of each one will get a (deserved) second season