-LRB- Sinagra -RRB- PUFFY AMIYUMI -LRB- Thursday -RRB- Hugely popular in Japan since the late 90 's , this two-girl anime tie-in duo , Ami Onuki and Yumi Yoshimura , sing spunky tunes that make J-pop ersatz of even the most prefab 60 's and 70 's American rock .