Okay well I could only find out how to write katakana with my keyboard so I had to use a little Photoshop magic! Now, I found that the kanji for 'watashi' is what was used. But the book spelled it out 'watakushi' so I'm confused, but other than that... here it is:
The stuff surrounded in blue is the tiny hirigana they used next to the kanji to spell it out.