Hotori has always tried to be a "good girl" and live her life without making waves. When she forgot to bring the survey book for her teacher Enjou, she tried to sneak back into the classroom at night, only to find a man asleep, surrounded by painting supplies. "So it was you!" Hotori ran away when the sleepy man suddenly kissed her. But the next day at school, she is reunited with that man Kodo, who claimed to be the new substitute art teacher... He is not the type you would usually call a teacher, with his impudent and slovenly attitude. At Enjou-sensei's request, Hotori is pushed into modeling for Kodo's paintings...... A pure but inappropriate after-school romance between a lazy art teacher and a "nice" high school girl. ずっと「いいこ」でいようと、波風立てずに生きてきた女子高生の歩鳥（ほとり）。 憧れの円城（えんじょう）先生に頼まれた集計用の名簿を忘れてしまい、夜に 忍び込んだ学校の教室で、絵の具に囲まれて眠る男性を見つける。 「あんただったのか」 寝ぼけた男性に突然キスされた歩鳥は逃げ出すが、翌日の学校で 非常勤の美術講師だという彼、胡堂（こどう）と再会してしまい──。 およそ先生と呼ばれるような人間ではなく、不真面目でだらしがない胡堂。 歩鳥は円城先生の頼みで仕方がなく、彼の絵画モデルをすることになるが……。 怠惰な美術教師と「いいこ」な女子高生の、純粋で不潔な放課後の恋。 「俺のモデルになるって、そういうことだよ――」