So the Iku Gundam and the oarfish unit combine into a literal support unit that is the "keystone" of Tenshi's tactics.
Nakae Iku's Personal MS: DD (Deep Diver)Transform & combine■Flying Platform
Keystone Mode
Carries Highlander
Flight-capableDD Messenger■Its role is to support Tenshi.
It's there for industrial purposes, but it flies using its piscine flight unit (left), and its special ability is controlling lightning.