Here's the intro riff, which we'll call Riff 1:
E|---------------------|
B|---------------------|
G|---------------------|
D|---------------------|
A|---------------------|
E|-1--1--4-5-6-6-7-8-2-|
At the beginning, just play this once every two bars, but after the little drum roll, 
play it over and over, consecutively, until Ayu starts singing. Then, just palm-mute this:

E|-----|
B|-----|
G|-----|
D|-3-3- At the beginning of each bar.
A|-3-3-
E|-1-1-

Then, when you get to the bridge (Tsurarete nemuku naru...), play:

E|------------------------------------|
B|------------------------------------|
G|-6--6--6--6--6--6--6--3--3--3--3--5-|
D|-6--6--6--6--6--6--6--3--3--3--3--5-|
A|-4--4--4--4--4--4--4--1--1--1--1--3-|
E|------------------------------------|
And after Ayu sings: "Just 1 LOVE", play this:

E|-----------------------|
B|-----------------------|
G|-----------------------|
D|-----------------------|
A|-4--6--1--3----1-2-3---|
E|-------------1-------2-|

Okay, and here's the chorus. It's VERY important that you play this fluently and 
and not harshly because otherwise it will sound very wrong. 8 strokes per bar, all down strokes.

E|-----------------------------------------------------------------|
B|-----------------------------------------------------------------|
G|-----------------3-3-3-3-3-3-3-3-6-6-6-6-6-6-6-6-8-8-8-8-8-8-8-8-|
D|-3-3-3-3-3-3-3-3-3-3-3-3-3-3-6-6-6-6-6-6-6-6-6-6-8-8-8-8-8-8-8-8-|
A|-3-3-3-3-3-3-3-3-1-1-1-1-1-1-1-1-4-4-4-4-4-4-4-4-6-6-6-6-6-6-6-6-|
E|-1-1-1-1-1-1-1-1-------------------------------------------------|
"Itsu datte nazeka retsu kara hamidashichau no ga atashi no shoubun"

E|---------------------------------------------------|
B|---------------------------------------------------|
G|-----------------3-3-3-3-3-3-3-3-----------------5-|
D|-3-3-3-3-3-3-3-3-3-3-3-3-3-3-3-3-5-5-5-5-5-5-5-5-5-|
A|-3-3-3-3-3-3-3-3-1-1-1-1-1-1-1-1-5-5-5-5-5-5-5-5-3-|
E|-1-1-1-1-1-1-1-1-----------------3-3-3-3-3-3-3-3---|
"Sasu nara togatta kotoba de gojiyuu ni osuki ni douzo mae ni nante"

Then, as Ayu sings: "na-ra-at-te", you palm-mute:
E|----------|
B|----------|
G|----------|
D|----------|
A|----------|
E|-6-4-6-7--|

Then play Riff 1 again, and continue through verse; bridge and chorus as normal. After 
chorus, instead of going back to Riff 1, play this:

E|---------------------|
B|---------------------|
G|---------------------|
D|---------------------|
A|---------------------|
E|-1--4--6-7-8--11-----|

When the lead guitar begins playing the solo, you play Riff 1, but three steps up, so:

E|-----------------------|
B|-----------------------|
G|-----------------------|
D|-----------------------|
A|-----------------------|
E|-4--4--7-8-9-9-10-11-5-|

Then back into the bridge and chorus. (The last chorus goes round twice). After the last 
play Riff 1 over and over, and end on the octave F.

E|----|
B|----|
G|-10-
D|-10-
A|-8--|
E|----|