Okay, well here's the riff you first hear at the beginning of the song. The only tricky 
is getting the power chords to go 3-3-1-3; but, to get around that, just don't let your 
be clumsy or sloppy (If that makes any sense :p).

E|---------------------------------------------|
B|---------------------------------------------|
G|----7--5-5-----------------5-7--5-5----------|
D|----7--5-5--5-5-3-5----7-7-5-7--5-5--5-5-7-7-|
A|----5--3-3--5-5-3-5----7-7-3-5--3-3--5-5-7-7-|
E|------------3-3-1-3----5-5-----------3-3-5-5-|

For the verse, just play:
E|---
B|---
G|-7-
D|-7-   At the beginning
A|-5-   of each bar
E|---   until Ayu sings:

"Itsu datte" Which is when you play it on every crotchet (So, every beat). But, only do 
for one bar, then do it on the in betweens (quavers) as well, and then the ones in 
those:

E|------------------------------|
B|------------------------------|
G|-7--7--7--7--7-7-7-7-77777777-|
D|-7--7--7--7--7-7-7-7-77777777-|
A|-5--5--5--5--5-5-5-5-55555555-|
E|------------------------------|

The rest just confused me... But I've known this beginning part for so long so I thought 
share it with other Ayu fans. ^_^