Please let me know about "Boost Mode Validity Period".
Boost Mode will be valid for one month after purchase.
After initial purchase, the Boost Mode subscription will renew automatically each month*.
You can review your subscription’s validity period via the methods below.
1. Tap Settings > [your name] > iTunes & App Store
2. Tap "Apple ID" at the top of the screen.
3. Tap "View Apple ID" then "Subscriptions"
4. Tap "Boost Mode" purchased on "SWORD ART ONLINE: Integral Factor"
to see the purchase history.
*Monthly period details:
・The subscription is valid until the same date in the following month from the last purchase or renewal.
Example) If the subscription was purchased or renewed on January 1st, it will be valid until February 1st.
・If there is no equivalent date in the following month, it will be valid until the closest date in that month.
Example) If the subscription was purchased or renewed on January 31st, it will be valid until February 28th.