I don't know if these matches you taste, but for me these are feel good songs
After School - Shampoo
Ami Suzuki - KISS KISS KISS
BoA - KEY OF HEART, Easy To Be Hard, M.E.P (My Electronic Piano)
Every Little Thing - Aigaaru
f(x) - Airplane
Girls' Generation - FLYERS, Way To Go!, VITAMIN
ICONIQ - Change Myself, Light Ahead, TOKYO LADY
Maaya Sakamoto - Himitsu, Kimi no Sei, Sayonara Santa, Remedy
Mika Nakashima - Memory
Narsha - Radio Star
Van Tomiko - Flower, message
Yuna Ito - Happy Days