From Peach Kyoudai:

Kouki had secretly loved Haru-nii, who used to live in the neighborhood when he was young. Five years later, despite Kouki making up his mind to move on, he unexpectedly gets reunited with Haru-nii as neighbors!

Although being invited to dinner or accidentally meeting outside gave him joy, Kouki couldn't help but feel dejected every time Haru-nii treated him like his younger brother. On top of that, the more they spent time together, his supposedly forgotten feelings bubble up even more!