Haruka  andMai,thank you.I know where I want to travel.Now I have to move forward to book hotel and ticket.It's troublesome,ha ha.

Oh, ok. Have a nice trip and take care! 

I am glad to hear that you want to go to Japan! Of course I recommend to you that you visit Kyoto and stay there for some days because there are many places we can enjoy seeing Sakura and Temples and cultures. I bet you can enjoy seeing both Sakura and historical street or building in Kyoto. What you should know is that there are a lot of people and some places need time to visit in Kyoto, especially spring and fall. I hope you can enjoy it! 

Easy access to see sakura spots- Okazakisosui (岡崎疎水), Nijouen (二条城), Shouseien (涉成園), Kyotogoen(京都御苑), and so on  http://www.japan-guide.com/e/e3951.html

not easy but beautiful..- Daigoji (醍醐寺), Haradanien (原谷苑), Arashiyama (嵐山)

I learned on internet that sakura will blossom abunduntly in Osaka and Kyoto .

I recommend Tokyo Tower and Skytree. You could see a lot from them.