bluntly
🇺🇸
/ˈblʌntli/
🇬🇧
/ˈblʌntli/
in a straightforward and honest way, without being tactful
To put it bluntly, I think your plan is flawed and needs a lot of improvements.
率直に言うと、あなたの計画には欠点があり、多くの改善が必要です。