Originally Posted by DragoZERO
Some guys act more mature around younger girls while others will act less mature. We know which one Junichi is.
You also have to remember that Junichi isn't the one furthering his relationship this time. Junichi already liked Haruka, and he was close enough to Kaoru.
Junichi simply wasn't *looking* for an intimate relationship in Sae's arc. He just helped Sae because she was a cute kouhai and only just realized that he has feelings for her when Sae asked to hold hands and participate in the couples contest. In Haruka and Kaoru's arcs, Junichi already harbored some feelings for them before the story began.