Bb                F7
/ / / / / /       / / / / / /

Just repeat this riff, and that's about the whole of the uke's role in Sea Breeze.

(Note: if you'll notice, when the camera zooms in on Ms. Mizuno's fingers, she doesn't finger the third fret of the A-string while playing [F7] on her ukelele, which is something to consider if you're trying to gain a similar sound).

A-------0---7---6------10---7----------0---7---6------10---7--------:
E---0------------------------------0--------------------------------:
C-------------------------------------------------------------------:
G-------------------------------------------------------------------:

A-------------------------------------------------------------------:
E---12~-----13---12---10---12~-----10---12~-----13---12---10---12~--:
C-------------------------------------------------------------------:
G-------------------------------------------------------------------:

~ = vibrato

Not a whole theme in particular, but the high-pitched riff that keeps showing up time and time again, minus that one note that even defies the high-pitched laws of a ukulele. I guess you could use a harmonic, in theory. If you want to just play that cool acoustic rhythm in the background, then fingerpick [Am], [Bm], and [Bbm].

 
A---5---8---5-------------------------------------------:
E---------------8---5---8---5-------------5-------------:
C-------------------------------5---7-7-------0---2-----:
G-------------------------------------------------------:

(English lyrics)

Chorus: One, two!

One-two Medicine is the best in Japan
Buy One-two Medicine
The medicine cures...
Pyrosis, stomach trouble, diarrhea
Dizziness before and after childbirth
Asthma, headache, influenza
Medicine can cure numerous illnesses
But no medicine can cure a fool
Foolishness is in heaps today
Japan is blooming with fools now
Suffer defeat, held under occupation
But fools call it the end of the war
Advocating democracy loud and clear
Only crooks throw their weight about
Bribery and corruption currently pass with impunity
Brazen fair and square
Scandals, paradise, a doodlebug trap
Those haughty fools never learn
Chirp and twitter all in unison
Chirp, chirp, twitter, twitter

A-------2-------0--------------0-------------------------------------:
E---0-------0-----------0----------4---3------3---2---0--------------:
C-------------------3------------------------------------------------:
G--------------------------------------------------------------------:

A--------------------------------------------------------------------:
E-------0---1---2----------0---1---2---------------------------------:
C---3------------------3---------------------------------------------:
G--------------------------------------------------------------------:

(repeat everything up to this point once)
========================================================

----------------------------------------
A----------------------------------------------0----------0---2---2--:
E---0-------0---2-------0---2---3------2---3----------3--------------:
C-------3------------------------------------------------------------:
G--------------------------------------------------------------------:
---------------------------------
A----------2---0-----------------------------------------------------:
E---0--------------3---2---0-----------------------------------------:
C--------------------------------------------------------------------:
G--------------------------------------------------------------------: