I'm on page 5 and I just wanted to say... Shouldn't it be "Shouko-chan"???????????
Although I can't find exact details, I think this is another system of Japanese romanization. It reminds me of the system in my old Japanese textbook that I stopped paying attention to because I learned romanization a different way.
No it's definitely a typo. It's either Sho(u)ko or Syo(u)ko, but not Shyoko (Hepburn vs Nihon-shiki/Kunrei-shiki romanization). Most common variant is Hepburn romanization. Regarding the "ou", you can either use "o", "ou" or "ō".