To enhance the WordPress default formatter’s flexibility, this plugin 
enables configuring content and excerpt styles with various formats.
<h4>Features</h4>
<ul>
<li>Replaces “br” tags with “p” tags.</li>
<li>Produces valid XML parser for all sources.</li>
<li>Automatically generates excerpts in chosen length. Enables configuring following settings; length, separator elements (period, 
touten, paragraph), read more text, tags which you allow in excerpts, 
and etc..</li>
<li>Add any tags or texts to one’s contents as header and footer.</li>
</ul>
<h4>Demo</h4>
See this plugin working on <a href="http://www.wembley.jp/" rel="nofollow ugc">my blog</a>. Contents and excerpts in this site are generated by this plugin.

Plastic Post Style

記事本文と抜粋の出力を調整・カスタマイズします。Configure content&excerpt styles of all posts with various configurations.

WPKube

FancyThemes

This plugin adds several improvements to WordPress’ default way of creating excerpts.
<ol>
<li>Keeps HTML markup in the excerpt (and you get to choose which tags are included)</li>
<li>Trims the excerpt to a given length using either character count or word count</li>
<li>Only the ‘real’ text is counted (HTML is ignored but kept)</li>
<li>Customizes the excerpt length and the ellipsis character that are used</li>
<li>Completes the last word or sentence in an excerpt (no weird cuts)</li>
<li>Adds a read-more link to the text</li>
<li>Ignores custom excerpts and use the generated one instead</li>
<li>Theme developers can use <code>the_advanced_excerpt()</code> for even more control (see the FAQ)</li>
</ol>
Most of the above features are optional and/or can be customized by the user or theme developer.
Banner image credit – <a href="https://www.flickr.com/photos/chillihead/" rel="nofollow ugc">chillihead</a>
Original plugin author – <a href="https://profiles.wordpress.org/basvd" rel="nofollow ugc">basvd</a>
Useful Resources
<ul>
<li><a href="https://fancythemes.com/what-is-wordpress/" rel="friend nofollow ugc">What is WordPress</a></li>
<li><a href="https://fancythemes.com/wordpress-themes" rel="friend nofollow ugc">Fee Themes</a> and <a href="https://fancythemes.com/wordpress-plugins/" rel="friend nofollow ugc">plugins</a></li>
</ul>

Advanced Excerpt

Control the appearance of WordPress post excerpts

Plastic Post Style vs Advanced Excerpt