It seems to be one of those things they missed when they added the Japanese in Banzai.
I would argue no for realism purposes and referring to rule 34.7 which prevents IG's from infiltration or (more germanely) berserking.
I always play as a IG may only be in a group by itself, like a AFV.
That is not the official rule (It would have been added in the Kickstarter edition), but I usually (always?) deploy an IG as a sole member of the group. I don't try to advance with an IG.
And it does solve this particular problem--since the IG could never be with a leader therefore it is not possible to banzai.
Having IG's in a group with other men causes issues with regards to banzai:
- Either IG's are allowed to banzai, as illogical as that seems.
- Or what happens if there group banzais and IG cannot? Do the (virtual) three (unarmed?) crewmen immediately appear? Is the IG (and its crew) simply eliminated (unlike a heavy Japanese weapon (45.6) which requires abandonment of the weapon, but primary & assistant crewmen attack in CC unarmed.