diff --git a/frontend/src/issues-list-board/issues-list-card.tsx b/frontend/src/issues-list-board/issues-list-card.tsx
index d66e243..fd05210 100644
--- a/frontend/src/issues-list-board/issues-list-card.tsx
+++ b/frontend/src/issues-list-board/issues-list-card.tsx
@@ -6,20 +6,24 @@ import * as TimePassedNs from '../misc-components/time-passed';
 import * as TagsNs from '../misc-components/tags';
 import * as IssueHrefNs from '../misc-components/issue-href';
 import * as IssueDetailsDialogNs from '../misc-components/issue-details-dialog';
+import * as UnreadedFlagNs from '../misc-components/unreaded-flag';
 
 export type Props = {
 	store: IIssueStore
 };
 
 export const IssuesListCard = observer((props: Props): JSX.Element => {
+	const unreadedStore = UnreadedFlagNs.CreateStoreFromLocalStorage(props.store);
 	const detailsStore = IssueDetailsDialogNs.Store.create({
 		issue: props.store,
-		visible: false
+		visible: false,
+		unreadedFlagStore: unreadedStore
 	});
 	return (
 		<div className={Css.listItem} onClick={(e) => {e.stopPropagation(); detailsStore.show();}}>
 			<IssueDetailsDialogNs.IssueDetailsDialog store={detailsStore}/>
 			<div>
+				<UnreadedFlagNs.UnreadedFlag store={unreadedStore}/>
 				<TimePassedNs.TimePassed params={{ fromIssue: { issue: props.store, keyName: 'timePassedClass' } }}/>
 				<span className={Css.issueSubject}>
 					<IssueHrefNs.IssueHref
diff --git a/frontend/src/kanban-board/kanban-card.tsx b/frontend/src/kanban-board/kanban-card.tsx
index 6babf0a..16f7b0e 100644
--- a/frontend/src/kanban-board/kanban-card.tsx
+++ b/frontend/src/kanban-board/kanban-card.tsx
@@ -6,6 +6,7 @@ import { getStyleObjectFromString } from '../utils/style';
 import * as TimePassedNs from '../misc-components/time-passed';
 import * as TagsNs from '../misc-components/tags';
 import * as IssueDetailsDialogNs from '../misc-components/issue-details-dialog';
+import * as UnreadedFlagNs from '../misc-components/unreaded-flag';
 
 export type Props = {
 	store: ICardStore
@@ -50,14 +51,17 @@ export const KanbanCard = observer((props: Props) => {
 			keyName: 'timePassedClass'
 		}
 	}
+	const unreadedStore = UnreadedFlagNs.CreateStoreFromLocalStorage(props.store.issue);
 	const detailsStore = IssueDetailsDialogNs.Store.create({
 		issue: props.store.issue,
 		visible: false,
-	})
+		unreadedFlagStore: unreadedStore
+	});
 	return (
 		<div className={KanbanCardCss.kanbanCard} onClick={(e) => {e.stopPropagation(); detailsStore.show();}}>
 			<IssueDetailsDialogNs.IssueDetailsDialog store={detailsStore} />
 			<div className={KanbanCardCss.kanbanCardTitle}>
+				<UnreadedFlagNs.UnreadedFlag store={unreadedStore}/>
 				<TimePassedNs.TimePassed params={timePassedParams}/>
 				<a href={props.store.issue.url.url}>{props.store.issue.tracker.name} #{props.store.issue.id} - {props.store.issue.subject}</a>
 			</div>
diff --git a/frontend/src/misc-components/issue-details-dialog.tsx b/frontend/src/misc-components/issue-details-dialog.tsx
index dc8982f..15c3fda 100644
--- a/frontend/src/misc-components/issue-details-dialog.tsx
+++ b/frontend/src/misc-components/issue-details-dialog.tsx
@@ -4,10 +4,13 @@ import { observer } from 'mobx-react-lite';
 import { Instance, types } from 'mobx-state-tree';
 import * as IssueHrefNs from '../misc-components/issue-href';
 import Css from './issue-details-dialog.module.css';
+import * as UnreadedFlagNs from '../misc-components/unreaded-flag';
+import { SetIssueReadingTimestamp } from '../utils/unreaded-provider';
 
 export const Store = types.model({
 	visible: types.boolean,
-	issue: types.frozen<RedmineTypes.ExtendedIssue>()
+	issue: types.frozen<RedmineTypes.ExtendedIssue>(),
+	unreadedFlagStore: types.maybe(UnreadedFlagNs.Store)
 }).actions((self) => {
 	return {
 		hide: () => {
@@ -17,6 +20,11 @@ export const Store = types.model({
 		show: () => {
 			console.debug(`Issue details dialog show: issue_id=${self.issue.id}`); // DEBUG
 			self.visible = true;
+			if (self.unreadedFlagStore) {
+				self.unreadedFlagStore.read();
+			} else {
+				SetIssueReadingTimestamp(self.issue.id);
+			}
 		}
 	};
 }).views((self) => {
diff --git a/frontend/src/misc-components/unreaded-flag.module.css b/frontend/src/misc-components/unreaded-flag.module.css
new file mode 100644
index 0000000..6bda63f
--- /dev/null
+++ b/frontend/src/misc-components/unreaded-flag.module.css
@@ -0,0 +1,16 @@
+.circle {
+	height: 6px;
+	width: 6px;
+	background-color: #707070;
+	border: 2px solid #707070;
+	border-radius: 50%;
+	display: inline-block;
+}
+
+.circle.unreaded {
+	border: 2px solid #0000FF;
+}
+
+.circle.forMe {
+	background-color: #FF0000;
+}
\ No newline at end of file
diff --git a/frontend/src/misc-components/unreaded-flag.tsx b/frontend/src/misc-components/unreaded-flag.tsx
new file mode 100644
index 0000000..f87da53
--- /dev/null
+++ b/frontend/src/misc-components/unreaded-flag.tsx
@@ -0,0 +1,64 @@
+import React from 'react';
+import Css from './unreaded-flag.module.css';
+import { observer } from 'mobx-react-lite';
+import { Instance, types } from 'mobx-state-tree';
+import { RedmineTypes } from '../redmine-types';
+import { GetIssueReadingTimestamp, SetIssueReadingTimestamp } from '../utils/unreaded-provider';
+
+export const Store = types.model({
+	issue: types.frozen<RedmineTypes.ExtendedIssue>(),
+	readingTimestamp: types.number
+}).actions((self) => {
+	return {
+		read: () => {
+			self.readingTimestamp = SetIssueReadingTimestamp(self.issue.id);
+		}
+	};
+}).views((self) => {
+	return {
+		getUpdatedTimestap(): number {
+			if (self.issue.journals) {
+				let lastComment: RedmineTypes.Journal | undefined;
+				for (let i = self.issue.journals.length - 1; i >= 0; i--) {
+					const journal = self.issue.journals[i];
+					if (journal.notes) {
+						lastComment = journal;
+						break;
+					}
+				}
+				if (lastComment) {
+					return (new Date(lastComment.created_on)).getTime();
+				}
+			}
+			return 0;
+		},
+		getClassName(): string {
+			let className = Css.circle;
+			const updatedTimestamp = this.getUpdatedTimestap();
+			if (self.readingTimestamp < updatedTimestamp) {
+				className += ` ${Css.unreaded}`;
+			}
+			console.debug(`Unreaded flag getClassName: issueId=${self.issue.id}; readingTimestamp=${self.readingTimestamp}; updatedTimestamp=${updatedTimestamp}; className=${className}`); // DEBUG
+			return className;
+		}
+	};
+});
+
+export function CreateStoreFromLocalStorage(issue: RedmineTypes.ExtendedIssue) {
+	const timestamp = GetIssueReadingTimestamp(issue.id);
+	return Store.create({
+		issue: issue,
+		readingTimestamp: timestamp
+	});
+}
+
+export type Props = {
+	store: Instance<typeof Store>
+}
+
+export const UnreadedFlag = observer((props: Props): JSX.Element => {
+	const className = props.store.getClassName();
+	return (
+		<span className={className} onClick={(e) => {e.stopPropagation(); props.store.read();}}></span>
+	);
+})
\ No newline at end of file
diff --git a/frontend/src/utils/unreaded-provider.ts b/frontend/src/utils/unreaded-provider.ts
new file mode 100644
index 0000000..685f86c
--- /dev/null
+++ b/frontend/src/utils/unreaded-provider.ts
@@ -0,0 +1,14 @@
+export function GetIssueReadingTimestamp(issueId: number): number {
+	const value = window.localStorage.getItem(getKey(issueId));
+	return value ? Number(value) : 0;
+}
+
+export function SetIssueReadingTimestamp(issueId: number): number {
+	const now = (new Date()).getTime();
+	window.localStorage.setItem(getKey(issueId), String(now));
+	return now;
+}
+
+function getKey(issueId: number): string {
+	return `issue_read_${issueId}`;
+}
\ No newline at end of file