Live and let live. (Shingeki no Kyojin) [English]
If you assumed that Eren and Levi had stressful relationships in anime series "Strike on Titans" then you just have not read this manga: even though this is a parody their eternal rivalry below is spruced up with sex and jelaousy! And not just sex yet yaoi sex! Plus things don't get any kind of simplier with the arrival of a third person who enters between them in greater than one definitions ...