ルーティングの修正。ログアウトが機能しなかったので、link_toからbutton_toに修正。

app/views/calendar/index.html.erb

@@ -1,5 +1,12 @@
 <h1 class="ui header">キャラクターカレンダー</h1>
 
+<% if user_signed_in? %>
+  <%= button_to 'Logout', destroy_user_session_path, method: :delete, class: "ui button" %>
+<% else %>
+  <%= link_to 'Login', new_user_session_path, class: "ui button" %>
+<% end %>
+
+
 <div class="ui buttons" style="padding-bottom: 10px;">
   <%= link_to calendar_index_path, class: "ui button primary" do %>
     <i class="calendar icon"></i> カレンダー

app/views/characters/index.html.erb

@@ -1,5 +1,12 @@
 <h1 class="ui header">キャラクター一覧</h1>
 
+<% if user_signed_in? %>
+  <%= button_to 'Logout', destroy_user_session_path, method: :delete, class: "ui button" %>
+<% else %>
+  <%= link_to 'Login', new_user_session_path, class: "ui button" %>
+<% end %>
+
+
 <div class="ui buttons" style="padding-bottom: 10px;">
   <%= link_to calendar_index_path, class: "ui button" do %>
     <i class="calendar icon"></i> カレンダー

app/views/home/index.html.erb

@@ -1,9 +1,7 @@
-<h1>Home#index</h1>
-<p>Find me in app/views/home/index.html.erb</p>
-
 <% if user_signed_in? %>
-  <h2>Welcome, <%= current_user.email %></h2>
-  <%= link_to 'Logout', destroy_user_session_path, method: :delete %>
+  <h2>ログイン中</h2>
+  <%= button_to 'Logout', destroy_user_session_path, method: :delete %>
 <% else %>
+  <h2>未ログイン</h2>
   <%= link_to 'Login', new_user_session_path %>
 <% end %>

config/routes.rb

@@ -1,7 +1,7 @@
 Rails.application.routes.draw do
-  get 'home/index'
+  # get 'home/index'
   devise_for :users
-  root to: "home#index"
+  root to: "calendar#index"
 
   # Define your application routes per the DSL in https://guides.rubyonrails.org/routing.html