-In Palmacosta, talk to the soldier outside the government building.
( The one to the right of the door.)
-After defeating the fake Summon Spirit on the altar in Asgard, you’ll
wake up in the expensive Asgard hotel. Go to Linar’s house to get Raine
back in your party. Then return to the same hotel you just stayed in
and pay 600 Gald to spend the night again. That night, Kratos will
offer another training session.
-After sneaking into the Asgard Human Ranch undercover and being saved
by Sheena, talk to the guy near the destroyed Weapon Shop. Kratos will
appear out of nowhere and say he wants to train again.
-When all the characters are standing in different points of Hima
before you go on the dragon trip to the Tower of Salvation, talk to
Kratos twice. This should activate the fourth and final event.