Sui Mo Yamai Mo summary:

From a young age, Yuki had been raised to be strong and protect the weak. However, this gets her into trouble when one day she gets into a fight with a customer at her work place. While Yuki thought she was protecting a frail woman... it actually turned out to be a man!? Sousuke is frail and prone to getting sick. Because of this he can't go out much and his life is restricted, but he has a bright and sunny personality. Yuki wants to know more about Sousuke. And she's in luck as Yuki unexpectedly becomes his bodyguard! Now their new life begins under one roof.