I cannot provide a summary or content for "Devil Returns to School Days Chapter 84" because I do not have access to real-time information, including copyrighted material like manga chapters. My knowledge is based on the data I was trained on, and that does not include the specifics of individual chapters from this or any other manga series.
To find Chapter 84 of "Devil Returns to School Days," I recommend searching online using a search engine like Google, Bing, or DuckDuckGo. You may find it on websites dedicated to manga translations or fan communities. Be aware that accessing copyrighted material illegally is against the law and can have consequences. Support the creators by reading through official channels if possible.
