This manga is something similar what happened to me at age 14. Me, sitting between two sisters on the same bed, both of them a little younger than me.
Younger girl kissed my cheek (falling all over me), then I kissed her older sister in a cheek, and then I returned kiss to younger (because I did not want her to feel lonely or neglected), and she kissed me back again, and I kissed her sister again (not to make her feel lonely or neglected as well), and all of us made many rounds of kissing (only in cheeks), in that room, on school vacation.
But I never called it "maternal instinct", like Akemi. I knew exactly what I feel and what I wish
(to kiss them in the lips), but we all were too shy to try, blushing with every kiss we shared.
Those were my blessed days of yuri. Then I found it all in manga, so many years after.
And now I see how blessed I was. And kissed so many times by two beautiful girls I liked.