This guide combines the official event teaser from October 3, 2026, the September 29 emergency-maintenance notice, and Producer's Letter #69 from September 25 into a shop priority list, a first-week sanity route, a preparation checklist and an October headhunt budget. Every date is taken from published official notices; estimates are marked as estimates, and exact values follow the official announcement. (This route is archived in the GameHub guides section.)
Applicable version: updated through 2026-10-03 (no version-number system; the official notice date is the time anchor)
Arknights "Yesterday's Sea" timing and first-week rhythm
The three confirmed dates
The official site posted "[Event preview] SideStory 'Yesterday's Sea' is coming soon" on 2026-10-03. Just before it, the studio published an emergency-maintenance notice on 2026-09-29 at 16:00 and Producer's Letter #69 on 2026-09-25. Over the past two years, Arknights has opened events roughly 3 to 7 days after a preview lands, which puts the launch window in early-to-mid October (estimate; follow the official announcement).
What the first week is really for
The first week is about unlocking and first-clears, not farming. Clear every stage once to bank the first-clear rewards, then work out which stage has the best token drop rate before committing sanity in week two (reasoning: first-clear rewards are one-time and cannot be recovered, while material stages can be farmed any day). The current store build is listed as v2.7.71 .
Arknights "Yesterday's Sea" event shop priority
The three must-buy categories
Three things sit at the top of the shop: the event-limited operator's tokens (used for potential), recruitment permits (which convert directly into pull value), and high-tier materials such as chips and polymerisation preparations. Even if you never raise the operator, tokens convert into universal tokens, which is why they rank first . Squad planning this month narrows to a Arknights best teams question: who covers the air lane and who clears waves.
What can wait
Furniture parts, low-tier battle records and Lungmen Dollars can wait. The test is simple: if you can farm it any day, it is not worth spending limited event currency on (reasoning).
| Buy order | Item | Why |
|---|---|---|
| 1 | Event-limited operator tokens | Converts to universal tokens |
| 2 | Recruitment permits | Direct pull value |
| 3 | High-tier materials | Chips and polymerisation, biggest gap |
| 4 | Module materials | Only if short |
| 5 | Furniture parts and LMD | Farmable, handle last |
Arknights October first-week sanity route
Where sanity comes from
Natural regeneration runs about 240 points a day, and daily missions plus the base push the usable total to around 400 points a day . Starting the stockpile three days early frees roughly 720 extra points for the event's first week.
Daily stage order
Fix the login order: claim mission rewards, run event first-clears, then spend any remaining sanity on the day's most efficient material stage. Do not spend it on the main story or resource stages during an event, because those can wait (reasoning).
Arknights "Yesterday's Sea" squad prep and low-cost positions
High ground versus ground
Iberia-themed stages have historically used a two-lane structure of ground push plus airborne harassment . Against two lanes, the most stable three-part setup is a high-block defender at the front, a damage dealer in the middle, and snipers and AoE casters on the back high ground. Elite-2 promotion needs chips and polymerisation materials, so bank 18 or more of each before the event (estimate; check the official material table).
Low-budget substitutions
Without a fully built defender, two mid-level operators can hold in two segments at the cost of one extra deployment slot. Pure single-target melee without anti-air value is a poor fit for the multi-wave structure expected here, so do not build one just for this event (reasoning: clear speed matters more than single-target ceiling in multi-wave stages).
Arknights October headhunt and Originite budget
The "lock one banner" math
October usually brings two banners. If you want both, at 6000 Originite per ten-pull you need at least 18000 points in reserve to call it safe (estimate). When resources are short, lock a single banner and move the rest of the budget into operator building, which is a more certain return.
How to read Targeted Selection
Targeted Selection lets you lock three six-stars out of six candidates. Decide by looking at the hole in your roster, not at a tier list . If your roster already covers anti-air and multi-target, there is no reason to pull for collection alone.
Arknights Yesterday's Sea stage prep and material checks
What an Iberia theme usually means for stages
Iberia is Arknights' long-running coastal region, and its past events have leaned on ground pressure plus airborne harassment . Expect at least one air lane and short gaps between waves, which is why anti-air coverage matters more than raw single-target damage here.
Which materials to pre-farm
Elite-2 promotion costs concentrate in chips and polymerisation preparations, so bank 18 or more of the mid- and high-tier items before launch (estimate; check the official material table). Pre-farming matters because the first week is better spent on event first-clears than on base stages, and the shop's high-tier materials only arrive once you start spending event currency.
How to read the shop against your roster
Do one inventory pass before the event opens. If you are short on chips, the shop's high-tier slot pays for itself; if you are short on a specific class's promotion item, farm that class's stage instead of buying generically. Matching the shop to your actual gap beats buying whatever looks scarce (reasoning: event currency is finite and the shop does not restock).More details can be found in the Arknights guide.
Arknights "Yesterday's Sea" FAQ
Q: When does "Yesterday's Sea" start?
A: The official site teased it on 2026-10-03, and Arknights normally opens 3 to 7 days after a preview, so expect early-to-mid October .
Q: What should I buy first in the shop?
A: Operator tokens and recruitment permits first, then chips and polymerisation materials; furniture and LMD last.
Q: How much sanity should I stockpile?
A: At least 1200 points. Natural regeneration runs about 240 a day, so starting three days early frees about 720 extra points.
Q: Should I pull for the new operators?
A: If your roster already covers anti-air and multi-target, you can skip. Wanting both banners means keeping at least 18000 Originite in reserve.
Action checklist
- Claim mission rewards daily and keep sanity above 1200 points.
- When the event opens, clear every stage once before farming.
- Buy in the order: tokens, permits, high-tier materials, furniture.
- Decide your AoE caster and sniper before launch and bank 18 or more key materials each.
- Lock one banner and keep an 18000-point Originite buffer.