When in the Japanese version 1.0 of Photoshop on the iPad, any Japanese text attribute that can be set in the desktop version of Photoshop are supported when opened on the iPad. However, none of those text attributes are editable. In some cases, importing or opening up a Photoshop document from Photoshop desktop can cause text reflow.
For 1.0, it is recommended that, for any documents that need rich text features and assets, you do your work in the desktop Photoshop version and not in Photoshop on the iPad. While Adobe is considering expanding the Japanese text feature set for future releases of Photoshop on the iPad, the current text tool set for Japanese is limited.