First time poster, long time reader of Excel Saga. Man, the things you miss until you read the things the umpteenth time.
I have't read the latest one yet, but I'm awaiting it's arrival with anticipation.
Now, as to my thoughts on Miwa:
1:maybe she's an android to replace the real Miwa, killed, sacrficed, or otherwise gone. Other than the friendship special incident, the seemingly unpredictable nature of the android personalities (Shioji mentioned that Ishiki's suffered due to the sensor load), and the thought that it'd be a great twist, I have no info to support this.
2:Maybe she actually IS Tenmangu. (sick but not entirely out of the realm of possibility.)
Things I DO know:
1:She and Tenmangu are convinced of Kabapu's story about the "Gate" etc... Meaning they have reason to believe it's true.
2:She has access to the same place that Excel and Hyatt stumbled into while wandering around the sewers looking for the entrance to the base.
Looking forward to continuing this.