Based on ep 261(?) if I'm not mistaken when they went to the haunted school to test their friendship with their VJs.

Ji Hyo was sitting restlessly beside her favourite muscular oppa as they waited for their turn to get inside the haunted school. Feeling her nervousness, Jong Kook put his arm around her small frame and pulled her closer to him. He knew how much she hated ghosts and not being able to go with her inside the haunted building was making him felt guilty. He so longed to go inside the school with Ji Hyo and protected her like how he always did but the PD made it clear that they could not go inside together.

So, as they nervously waited for their turns, he approached Gary and asked him to take good care of Ji Hyo. it was not because Gary would leave Ji Hyo alone in the building and save only himself, but the thought of his woman being left alone in that scary-looking building was really disturbing the commander.

'Don't worry, hyung! I'll guard her with my life, I promise.'

Ji Hyo chuckled hearing Gary's promise to Jong Kook. She approached the two men and leaned closer to her oppa. She was really nervous about having to go inside the haunted school and she wanted her man's calmness to rub on her so that she would be able to complete the mission. 

'You better keep your promise, Gary oppa!'

Gary nodded solemnly. Yes, it was just a game and it would probably be safe enough for all the casts and crews to film there but the scary setting was making Gary serious. He worried a lot about getting inside there with Ji Hyo but he also couldn't let her go in with Suk Jin for fear that t