Is I Don't Understand What My Sister's Friend Is Thinking Worth Reading? Review & Where to Read

Overview

I Don't Understand What My Sister's Friend Is Thinking follows Yuuto Hidaka, who's spent years mystified by Tsuyu Amemiya — his little sister Chie's quiet, perpetually unreadable best friend, who's practically part of the family at this point. Tsuyu has feelings for Yuuto that she's never been able to put into words, and the manga spends its short, complete run tracing how those feelings slowly become visible to him, one small gesture at a time.

What it does well

The manga's whole appeal rests on its patience, and it earns that patience. Rather than building its romance around big confessions or dramatic misunderstandings, it lets Tsuyu's feelings surface through small, specific details — the kind of thing you'd only notice if you were paying close attention, which is exactly the position the story puts Yuuto in. That restraint makes the eventual emotional payoffs land harder than a louder, more conventional approach would.

Both leads feel like genuine people rather than romance-manga types. Tsuyu's quietness isn't played as a quirky gimmick; it's treated as a real part of who she is, and the manga is careful to show readers (if not always Yuuto) what's going on underneath it. Chie, meanwhile, is a real asset to the cast — she's in on more than Yuuto realizes, and her presence keeps the story feeling like it's set in an actual social world rather than an isolated two-person romance bubble.

Where it falls short

The same understated approach that makes the series work will be a drawback for readers who want their romance manga to deliver bigger, louder moments. This is a quiet book, and it stays quiet even at its most emotionally significant points — which is by design, but won't land for everyone. The small cast and low external stakes also mean there isn't much conflict driving the plot beyond the central relationship, and a few side characters introduced along the way don't get much room to develop in just three volumes.

Verdict

I Don't Understand What My Sister's Friend Is Thinking is a quiet, well-observed high school romance that trusts its readers to pick up on the same small details its protagonist is slowly learning to notice. It won't satisfy readers looking for melodrama, but as a complete, patiently told story about learning to really see someone, it's a genuinely satisfying read.