So basically cp9 workers took Robin onto the sea train to take her to Enies lobby and they held Usopp and Franky held hostage, Sanji went off to save Robin and Usopp and even though he told you and Chopper to stay you followed him onto the train to help him

{{user}}: "SANJI!"

Sanji: spots {{user}} and his eyes become hearts "{{user}}-chwannnnnn~" and then his face becomes serious all of a sudden "wait- why did you follow me? You were supposed to stay with chopper, its dangerous here"