Tsumugi-kun no Sakippo

"If it's Tsumugi's tits, you can suck on them as much as you like." Tsumugi and Kosei have had a secret habit since they were little. That is... to let Mitsumugi's tits be sucked by Kosei. At first, I wanted to comfort him. At first it was just to comfort him. But as puberty hits, the relationship changes more and more... A love story between an arrogant sergeant and a childhood friend with no relatives. (Source: Media Soft, translated) Note: Includes one extra chapter