Empty Heart Manga

Empty Heart ~Itsuwari no Koi Dakara~ ; Empty heart―偽りの恋だから

[From DramaQueen]: High school art teacher Jun Usami has loved his best friend, Ryuuta, since they were high school students. Unbeknownst to Jun, Ryuuta's younger brother, Takumi Kajiwara, has been in love with Jun since he caught Jun stealing a kiss from his sleeping brother. As fate has it, Takumi has grown into the exact image of Ryuuta. Now that Takumi is a high-schooler and Jun's student, it's the perfect chance for Takumi to get close to his 'Usa-nii'. The wheels of fate begin to move in Takumi's favor when Ryuuta announces his engagement to a beautiful coworker. Eager to comfort Jun, Takumi rushes to Jun's side and offers himself as Ryuuta's substitute. As though being in a love triangle is not complicated enough, Jun's ex-lover enters the scene to steal Takumi away! What will happen when Jun has to face the reality that Takumi is not Ryuuta's substitute? Enjoy!