Kurayami ni Strobe by Hayakawa Nojiko
Arata who is in love with his childhood friend Miyamoto, always eavesdrops on the confessions his friend receives from girls but Miyamoto constantly rejects the confessions saying he already has someone he likes. One day Miyamoto catches Arata eavesdropping and asks, “Want to know who?”
That question got me into reading this manga. A funny, heartwarming manga full of shounen-ai goodness.