Ciphertext manipulation for ciphers with intermediate tags
As the specification of Keyak v2 explains:


  To produce a tag that depends on the full message and not only on the message bits that have been injected in a single duplex instance, Motorist
  performs some dedicated processing at the end of each message called a knot. It extracts
  chaining values from each duplex instance, concatenates them, and injects them into all
  duplex instances. This makes the state of all duplex instances depend on the full sequence
  of messages. Then it extracts a tag from a single duplex object.


right within chapter 1 (emphasis mine). Note that Motorist is the underlying construction of Keyak 2.