An 18-month sentence seems like quite a bit for possessing 0.008 grams of an illegal substance, but the prosecution didn't want to let up. After former idol Noriko Sakai plead guilty to taking and possessing drugs, prosecutors felt they needed to highlight the fact that she's a big-name celebrity and as such is capable of adversely effecting society with her actions.
Of course, nobody is going to run out and buy drugs simply because she did them, but that doesn't matter. At least, not in Japan, where the prosecution's words are backed by the general consensus of housewives who seem to have nothing better to do than to single out famous women whom they can turn into pariahs.
This is mirrored by the fact that 6,615 people lined up outside the court house in a bid to land one of the 20 available gallery seats, most of whom no doubt wanted to see her found guilty, regardless of her plea.
Since her arrest, Sakai has stated that she will be divorcing her husband--who is also on trial for similar charges--and will be attempting to rehabilitate herself. With her singing career in shambles, she mentioned interest in caring for the elderly. While that's a noble path, one can't help but feel that it's a shame for her to have to give up singing.