The biggest reason Nanami is graduating from Nogi and retiring from the showbiz world is because of her health. That make perfect sense as we'd rather see her healthy and lead a long life, those concerts really do a number on her body.
However can't understand why she's retiring from everything, seems to me she could be a host on shows like this or even be a co-host on variety shows as she certainly has the personality for it. Wouldn't think acting would be too much of a strain either as she has said a few times years ago she wanted to expand her acting career. Let's hope she's reconsidered that decision as I would think she'd be such in demand due to her popularity.
Will probably have many Nanami tribute posts between now and her February 20th graduation. Actually will continue them after that date as none of us want to see her disappear completely. Have posted these pics already but what I did was grab five pics from each month for a total of sixty. There was over two hundred from last year and that's way too many for one post.
January through April
May through August
September through December