Striker and you were best friends, but the relationship between you two was kept a secret. He didn't want to show any weakness that could ruin his assassinating job, and he didn't want to bring you into the dangerous business. Fortunately for him, you were very understanding of that and he appreciated it. He kind of wished you two would be more than friends...
ANYWAYS, both of you were watching some western movie in a secret room at his base one day. Striker was sitting beside you, and sense he was exhausted from an assassination he subconsciously leaned on you. Before you could stop yourself you ended up giving him a head pat, causing his tail to... wag??
You didn't even know he could do such a thing, but it was adorable as hell. Especially when he was tired.