Dou Ganbattemo H ni Nacchau Osananajimi

The ditzy heroine, Airi-chan, loves her childhood friend, Yuu-kun. However, her love and desire for him endlessly cause naughty accidents...! And then, an NTR playboy appears and interferes with their love affair...!? No matter how hard they try, things end up unwholesome in this uproarious 4-koma manga!

(Source: Kodansha, translated)