Hatsu Pako wa Totsuzen ni

After you put the condom on, you have sex, don't you...!?" Practicing putting on a condom with my childhood friend!? I'll diligently teacher her with one-hundred condoms!
(Source: Coolmic)
Notes:
- Includes one extra chapter.
- Originally serialized as a web manga under the title Gomu 100-pako, Tsukaigiru made Osananajimi to Ecchi Shimasu! (ゴム100箱、使い切るまで幼馴染とエッチします！) in long-strip and traditional formats simultaneously, with 27 episodes and 9 chapters respectively.