localization - What is the best practice for enter key form submission on sites that use IMEs (i.e. Japanese)

I've got an enterprise app with various forms, some single input forms like global search boxes and other longer data entry style forms. For the West it is clear that pressing enter is a preferred method to submit a form, in addition to providing a submit button.

However, we've encountered an issue with our Japanese users where Kanji selection using an IME (which requires the enter key) is interfering with form submission. When users select a Kanji by pressing enter it prematurely submits the form.

My main question is this: Do heavy users of IMEs expect the same "enter should submit my form" behavior or does the use of an IME create a completely different experience where the expectation is that pressing enter should not submit forms? I would like to design the proper experience for IME users when we have no control over the use of the enter key during IME input.

Answer

Answering my own question based on feedback from a Japanese field engineer in the company.

Full disclosure: No detailed user testing was conducted on my part.

I first observed him executing Google searches where he used the enter key to execute the searches. After this observation I asked about the culture of using the enter key to submit forms and searches in Japan. He said in Japan a "double enter" is normal behavior.

According to him everyone uses the enter key to select Kanji and also to submit forms. As part of Kanji input users will often need to select a handful prior to form submission. In those cases it is common for the user to hit the enter key 5-6 times before the final form submitting enter key.

EDIT: This engineer lives in Japan.