<header>
    <nav class="navbar navbar-dark bg-primary">
        <a href="#" class="navbar-brand lht-0">
            <i class="fas fa-chevron-left fs-12 p-1"></i>
            <span class="d-none d-md-inline fs-10">
                戻る
            </span>
        </a>
            <div class="navbar-nav">
                <div class="nav-item">
                    <div class="text-size btn-group btn-group-sm" role="group">
                        <button type="button" class="btn btn-white btn-sm border size-button smaller"><i class="fas fa-minus"></i></button>
                        <button type="button" class="btn btn-white btn-sm border size-button defaulter"><i class="fas fa-font"></i></button>
                        <button type="button" class="btn btn-white btn-sm border size-button larger"><i class="fas fa-plus"></i></button>
                    </div>
                </div>
            </div>
    </nav>
</header>