Lyrics, arrangement, and everything under the sun by Miyavi
Romaji lyrics by Yilei (Me)

A-ha-ha* Ashita waratte rareru you ni
A-ha-ha* Kyou kara waraou

Ashita, waraeru you ni...
Kimi to waraeru you ni...
Zutto waraeru you ni...

Hito wa warai jiwa no kazu dake shiawase ni nareru to omoundesu.

"Tsura"i toki mo saa mou ippon,**
Warai jiwa taseba hora "shiawa"se sa.

A-ha-ha* Ashita waratte rareru you ni,
A-ha-ha* Waratte waratte Be with a smile.***

Haguki zenkai de i-janai, hanage de tetatte i-janai.
So laugh away

Ashita, waraeru you ni...
Kimi to waraeru you ni...
Zutto waraeru you ni...

Ashita no koto bakari nayandenaide
Hore, do-senara motto motto dekkee mirai no koto nayamimasho.

A-ha-ha* Ashita waratte rareru you ni, ima waraou.****

A-ha-ha* Ashita waratte rareru you ni,
A-ha-ha* Waratte waratte, hora waratte waratte, motto waratte waratte,*****
Noutenki ni natte bakannatte Yeah

Ashita, waraeru you ni...
Kimi to waraeru you ni...
Zutto waraeru you ni...

*It actually sounds like he's saying "Ah ha Ah ha" three times rather than what's written.
**Here afterward it sounds like he's laughing "Ahehahehan hehan hehan"
***Before the waratte it sounds like he sings "So". He repeates waratte waratte again afterward though and between the first set and the second it sounds like he's saying "and". Then right before he goes into "Be with a smile" he seems to say "So I". Then "Oh Be with a smile". Thus the line sounds like "So waratte waratte and waratte waratte. So I...Be with a smile. Oh Be with a smile."
****Be sure to add the A-ha-ha before the waraou here. It's in place of the "ima" but in the lyrics it's written this way.
*****Right before the waratte waratte again it sounds like he says "So"