True friends are never apart (book 4)

Its been Five years since the incident in Washington. Rona got her memories of leon back. Her and leon have been together for five years and there Relationship has only grown stronger and Leon thinks its time to take the next step but their romantic time gets cut short and have to go on a mission to the eastern slav republic. When they get there they get told to go back not wanting to waste their time they stay and continue their mission on their own. (read your my best friend, best friend's always stay together and remember me before reading)