This is the classic decision people "feel out" and get wrong for years. The per-meal difference is small enough to ignore — which is exactly why it compounds. Mio doesn't care about willpower. Here's the math, and the honest exception.
A cheap eat-out meal in Japan — a gyudon bowl or a konbini bento — is often ¥500–800 (illustrative). Cooking the same rough meal at home lands around ¥200–350 once you buy rice, a protein, and a vegetable in normal supermarket portions. So the per-meal gap is roughly ¥300–450. Small. Forgettable. That's the trap.
| Assumption | Value |
|---|---|
| Eat-out lunch (gyudon / konbini bento) | ¥600 |
| Home-cooked equivalent | ¥250 |
| Per-meal difference | ¥350 |
| Workday lunches per month | 22 |
| Monthly gap | ¥350 × 22 ≈ ¥7,700 |
| Yearly gap | ≈ ¥92,000 |
So the decision isn't "¥600 vs ¥250." It's roughly ¥90,000+ a year for one meal a day, before you even count dinner. That's the whole point of running the number instead of feeling it.
Here's what the ¥250 figure quietly assumes — that you actually eat everything you buy. For a busy solo person, that assumption often breaks:
Food waste for one. Supermarkets sell in family portions. A cabbage, a pack of meat, a bag of vegetables — a solo cook frequently can't finish them before they spoil. If a third of your groceries hits the bin, your "¥250 meal" is really ¥350–400, and the gap shrinks fast.
Time cost. Shopping, prep, cooking, and cleanup is real time. If you value your hour at even a modest rate, a 30–40 minute home meal has a cost the ¥250 never shows. A gyudon bowl is 5 minutes, start to finish.
Break-even logic: jisui wins clearly when you cook in batches, finish your ingredients, and don't price your time highly. It loses when you cook single small portions, waste a chunk, and are time-poor. If you'd realistically waste ~30% and only cook a few times a week, the honest answer can be: a mix, not full jisui.
Half-price (半額) evening discounts. Many supermarkets sticker down bento, meat, and fish in the last hour or two before closing. Shopping then can cut a home meal's cost sharply — and closes the waste gap because you're buying what you'll cook tonight.
Gyomu super for bulk. Business-supermarkets (gyomu sūpā) sell frozen and bulk staples cheaply. These only pay off if you have freezer space and actually work through them — bulk that spoils is just slower waste.
Cook to finish, not to portion. Batch-cook the whole pack, freeze or eat within days. The single biggest lever for a solo cook isn't buying cheaper — it's not throwing food away.
If you'll cook in batches and finish your ingredients → jisui wins, and by a lot (~¥90,000+/year on lunches alone). If you're time-poor, cook tiny solo portions, and waste ~30% → the gap collapses, and a mix of cheap eat-out plus some cooking can be the rational answer. The "right" choice isn't discipline — it's whether your kitchen actually converts groceries into meals instead of trash.