These are the packages that would be merged, in order:

Calculating dependencies ... done!
Dependency resolution took 1.09 s (backtrack: 0/20).

[ebuild  N     ] acct-group/groonga-0-r2::gentoo  0 KiB
[ebuild  N     ] dev-libs/onigmo-6.2.0-r1:0/6::gentoo  USE="-combination-explosion-check -crnl-as-line-terminator" 826 KiB
[ebuild  N     ] dev-cpp/xsimd-14.3.0::gentoo  USE="-doc -test" 371 KiB
[ebuild  N     ] dev-cpp/jsoncons-1.6.0::gentoo  USE="-test" 1566 KiB
[ebuild  N     ] acct-user/groonga-0-r2::gentoo  0 KiB
[ebuild  N     ] dev-libs/simdjson-5.0.5:0/34::gentoo  USE="all-impls -nan -test -tools" 15150 KiB
[ebuild  N     ] app-text/mecab-0.996-r2::gentoo  USE="unicode -static-libs" 1366 KiB
[ebuild  N     ] app-dicts/mecab-ipadic-2.7.0.20070801-r1::gentoo  USE="unicode" 11922 KiB
[ebuild  N     ] app-text/groonga-16.1.0::gentoo  USE="json mecab -apache-arrow -blosc -curl -debug -libedit -lz4 -msgpack -stemmer -suggest-learner -xxhash -zstd" CPU_FLAGS_X86="avx avx2 avx512dq" 101264 KiB
[ebuild  N     ] app-text/groonga-normalizer-mysql-1.1.1-r1::gentoo  536 KiB

Total: 10 packages (10 new), Size of downloads: 132998 KiB