You are drenched by 9 a.m. and the day has not even started.
You ducked into the bathroom to wipe down before the morning meeting. You layered a black undershirt, you stuck a sweat pad on the back of your collar, and the patches still bled through. The aircon is on. Everyone else looks dry. You are convinced something is wrong with you specifically.
I have watched person after person move to Japan and quietly conclude they are broken. They are not. They just walked into one of the most punishing summers on earth with none of the local cheat codes. Japan does not sweat less. It just prepares more.

Here is the thing nobody tells you in your first June here. A Tokyo summer is not "hot." It is a wet wall. Thirty-four degrees with humidity in the high seventies means your sweat has nowhere to evaporate, so it just sits on your skin and soaks your shirt.
Locals are sweating too. The salaryman next to you on the train has a towel in his bag for a reason. The reason you feel like the only swamp in the room is that you grew up somewhere where visible sweat reads as a personal failure. That story does not travel well here.
In Japan, dabbing your face with a folded handkerchief on the platform is just a normal Tuesday. The patches bother you far more than they bother anyone looking at you.
Walk into any drugstore in July and there is an entire wall built for exactly your problem. Most newcomers walk right past it because they do not know what they are looking at.

A few things locals reach for without thinking:
None of this is secret. It is just invisible until someone points at the right shelf and says "get that one, not that one."
Here is the part that actually matters for a physical job. If you are on your feet all day in thick uniform fabric, no antiperspirant on earth will save you. You are fighting the wrong battle.
What Japanese tradespeople, delivery crews, and warehouse staff use is the 空調服, a work jacket with little fans sewn into the lining that pushes air across your whole torso. They are everywhere on construction sites in August for a reason. There are also cooling vests, ice packs that slot into special undershirts, and breathable replacements for exactly the kind of stiff polo that is betraying you right now.

You will not find any of this by Googling in English. You find it because a coworker mentions it, or a friend drags you to a Workman store and shows you what actually works.
Notice the pattern. Every fix above is one casual sentence from a local away. The wipe brand, the cooling fabric, the fan jacket, the "honestly nobody is looking at you the way you think" reassurance. None of it is hard information. It is just trapped on the other side of a conversation you are not having yet.
That is the quiet tax of doing your first Japanese summer alone. You suffer through problems that any local would have solved for you in thirty seconds, because you do not have anyone to ask the small embarrassing questions. Isolation makes every problem heavier than it is.
This is the gap SewaYou was built to close. It is a map-based app that shows you the actual people near you who are open to meeting, locals and fellow newcomers alike, so the person who knows which shelf to point at is someone you can actually message.

A real friend nearby is worth more than a perfect antiperspirant. They tell you about the fan jacket. They tell you which station has the good aircon. They tell you, the first time you apologize for sweating, to stop apologizing, because everyone here is doing the exact same thing.
You can survive a Japanese summer on grit and Daiso pads. It is so much easier with someone who already knows the map.
Download SewaYou and find the people near you who can actually help you live here, one small question at a time.