Locate under ~/.config/karabiner/assets/complex_modifications/

karabiner_elements_aquaskk_on_iterm2.json

{
    "title": "AquaSKK on iTerm2 / Terminal.app",
    "rules": [
        {
            "description": "Change left_ctrl + j to Hiragana on iTerm2",
            "manipulators": [
                {
                    "conditions": [
                        {
                            "bundle_identifiers": [
                                "^com\\.googlecode\\.iterm2$",
                                "^com\\.apple\\.Terminal$"
                            ],
                            "type": "frontmost_application_if"
                        }
                    ],
                    "type": "basic",
                    "from": {
                        "key_code": "j",
                        "modifiers": {
                            "mandatory": ["left_control"],
                            "optional": ["any"]
                        }
                    },
                    "to": [
                        {
                            "key_code": "japanese_kana",
                            "modifiers": [
                            ]
                        }
                    ]
                }
            ]
        }
    ]
}