JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://rawgit.com/masayuki0812/c3/master/c3.js"></script>
<link rel="stylesheet" href="https://rawgit.com/masayuki0812/c3/master/c3.css">
<div id="chart1"></div>

CSS

.report {
    width: 10px;
}

JavaScript

c3.chart.internal.fn.additionalConfig = {
    bar_radius: 18
};

c3.chart.internal.fn.isOrderDesc = function () {
        var config = this.config;
		if(this.isFunction(config.data_order)) {
			return false;
		}else {
			return config.data_order && config.data_order.toLowerCase() === 'desc';
		}
};


c3.chart.internal.fn.isOrderAsc = function () {
        var config = this.config;
        if(this.isFunction(config.data_order)) {
			return false;
		}else {
			return config.data_order && config.data_order.toLowerCase() === 'asc';
		}
};

c3.chart.internal.fn.generateDrawBar = function (barIndices, isSub) {
        var $$ = this, config = $$.config,
            getPoints = $$.generateGetBarPoints(barIndices, isSub);
        return function (d, i) {
            // 4 points that make a bar
            var points = getPoints(d, i),
				groups = config.data_groups,
				path = '';

            // switch points if axis is rotated, not applicable for sub chart
            var indexX = config.axis_rotated ? 1 : 0;
            var indexY = config.axis_rotated ? 0 : 1;
			
			if(groups && groups.length>0) {
				var lastGrps = [],
                    bar_radius = config.bar_radius;
				groups.forEach(function(group){ 
				   lastGrps.push(group[group.length-1]);
				})
				if(lastGrps.indexOf(d.id) > -1 && (config.data_order === null)) {
					if(config.axis_rotated) {
						path = 'M ' + points[0][indexX] + ',' + points[0][indexY] + ' ' +
							'L' + (points[1][indexX]-bar_radius) + ',' + points[1][indexY] + ' ' +
							'Q' + points[1][indexX] + ',' + points[1][indexY] + ' ' + points[1][indexX] + ',' + (points[1][indexY]+bar_radius) + ' ' +
							'L' + points[2][indexX] + ',' + (points[2][indexY]-bar_radius) + ' ' +
							'Q' + points[2][indexX] + ',' + points[2][indexY] + ' ' + (points[2][indexX]-bar_radius) + ',' + points[2][indexY] + ' ' +
							'L' + points[3][indexX] + ',' + points[3][indexY] + ' ' +
							'z';
					}else {
						path = 'M ' + points[0][indexX] +...