David Schuttenberg explains that Kewpie is emulsified into "a perfectly creamy, tight sauce" while other brands tend to be over emulsified, which results in a "gloopy, overly thick consistency." ...

You can mix it in at the same time as the flavor packet, or, alternatively, you can mix the Kewpie ahead of time with the flavor packet to create a separate sauce. In the latter case, be sure to ...