Well, I didn't really know what this song was about - but I really enjoyed watching all the shadow puppets in the video...makes me want to go tent camping. It's called "Tsubomi" ("bud") by Kobukuro, and it was the number one song in Japan last year. Here are the lyrics (up to the chorus) in romaji - so now you can sing along! :) (For any of you that KNOW Japanese - I just found these on the internet - forgive any mistakes!)
Namida koboshitemo, ase ni mamireta egao no naka ja.
Daremo kizuite wa kurenai
dakara anata no namida wo boku wa shiranai.
Tayasu koto naku, boku no kokoro ni, toosareteita
yasashii akari wa anata ga kureta riyuna ki ai no akashi.
Yawarakana hi damari ga tsutsumu senaka ni potsuri hanashikakenagara.
Itsuka konna hi ga kuru koto mo
kitto kitto kitto wakatteta hazu na noni.
Kiesouni, sakisou na, tsubomi ga kotoshi mo boku wo matteru.
tenohira ja, tsukamenai kaze ni tooru hanabira.
tachitomaru ni kata ni hirari
jouzu ni nosete waratte miseta anta wo omoide su hitori.