style.json

{
    "version": 8,
    "metadata": {
        "test": {
            "pixelRatio": 2,
            "localIdeographFontFamily": "sans-serif",
            "width": 800,
            "height": 600
        }
    },
    "zoom": 8,
    "sources": {
        "sample": {
            "type": "geojson",
            "data": {
                "type": "Feature",
                "geometry": {
                    "type": "Point",
                    "coordinates": [0, 0]
                },
                "properties": {
                    "name_en": "a-b,c.",
                    "name_ja": "あーい、う。"
                }
            }
        }
    },
    "glyphs": "local://glyphs/{fontstack}/{range}.pbf",
    "layers": [
        {
            "id": "sample-text-left",
            "type": "symbol",
            "source": "sample",
            "layout": {
                "text-anchor": "top",
                "text-field": "{name_ja}{name_en}",
                "text-font": ["Open Sans Semibold", "Arial Unicode MS Bold"],
                "text-size": 30,
                "text-offset": [0, -2]
            }
        }
    ]
}