The mangaka first had the MC's eyes on Suzuho (the oneesan) alone, while justly deriding the pedobait as completely beneath that sort of attention from him; then one chapter came around and now he can't resist the "DFC", as the pedos call it, and is constantly picked on by the pedobait. Now he's somehow spineless and helpless before her.
You'd think this manga was made in like 2012 with the characters playing systems like the Wii and DS (page 10), not that I mind, I think more mangas should bring back the oldies.