Ane no Yuujin

Hinako, a friend of Asahi's older sister, is a frequent guest at the home of the high school boy. She always misleads his mind with her suggestive attitude while treating him like a little brother...or rather, pet? A love story between a gal who has a bugged sense of proximity and an otaku guy who acts like her parent!

Chapters 3 and onwards can be found in the serialised version