Love Lab

From Shoujo Manga Maniac:

1) Love Lab
The chemistry club invented a special hormone potion. Each bottle cost 500 yen. Riko-chan's boyfriend, Yuuki-kun himself is extremely cold towards love. Riko-chan hopes to move their relationship one step ahead, but in the end...?

2) Merry Kiss

3) Perfect Doll

4) Twinkle Twinkle

5) Cupid's Arrow