People make a huge deal about how Jyou and Yamato are selfless enough to throw themselves under the bus for the sake of the other kids, but here we have Koushiro of all characters offering himself up to Etemon as villain bait. The kid doesn’t get enough credit for it, but he is incredibly brave, and unlike the other two, he isn’t fucking reckless about this sort of decision—he planned to sacrifice himself and Tentomon from the very beginning, and did so in a way that would leave him reasonably certain that Taichi had all the time and information he needed to rescue Sora.
It’s all rather horribly pragmatic. Koushiro wrote the kids’ rescue plan more or less by himself, and it goes like this: the others would attack the base from the outside to lure Etemon out, and once Etemon had found them, they were all supposed to IMMEDIATELY turn tail and retreat. Even if that meant Etemon might figure out what was going on, and head back inside once he realized a few of the children were missing.
And that’s exactly what Etemon did. He went back in, to find the ones who had infiltrated and try to beat Nanomon’s location out of them. Koushiro wrote the plan so that he was the only one of the kids that would enter the pyramid alongside Taichi. Because someone needed to be able to stall for time, in the event that worst came to worst. And he likely knew that it would.
Koushiro wrote this plan so that six of the kids would hopefully survive.