Xcomp gives it 75%
Exiting the detective agency (Rinas home), you find there are 6 places to visit including the shopping district and park along with a few others greyed out at first. Once you enter a location, investigations involve going around speaking to NPCs and collecting various items just as you would expect from an adventure game. A lot of the times, Jii will be giving advice or working on some strange new invention of his to help Rina which sometimes requires you to collect some materials for him. Unfortunately, Rinas head doesnt turn towards items you can interact with unlike some of the modern PC titles so this means youre back to the traditional way of pixel hunting.

Rina and the vampire butler, Jii at home.
When speaking with NPCs, dialogues appear in rectangular speech bubbles and you are given a multiple choice of subjects to speak about, moving the story along. Characters often respond with some expressive animation, punctuation mark or light bulb above their heads which is fairly entertaining to watch. Especially those little skull shaped puffs of smoke that comes out of their angry heads.
You can play via buttons or stylus although the latter would be best recommended for this type of point and touch adventure game. The top screen shows a picture of Rina and the name of the current place youre in along with the thoughts Rina has as you speak to various characters, giving you a clue about what you maybe looking for from them. Even so, I found myself ignoring the top screen most of the time.

Read Rinas mind.
On the other hand, the bottom screen is where the menu and your inventory are. There is a bar that holds items you find as well as a notepad that allows you to access the main menu, where you can save, load or return to the title screen. A hand allows you to de-select any item you have selected. Double-tapping on any of the items allows you to view them in more detail which in some cases, allows you to take apart an object, e.g., untying a ribbon from a bag of cookies. You can also combine items too and the interface seems to work very well.

Spider in the net. Want to clean it out?
Having played many PC adventure games from the first Monkey Island to Syberia and Run Away Adventure, I found that Osawari Tantei doesnt take too long to complete should you decide to only run through the main cases. The four cases took just under 10 hours or so to complete and because you dont get a grade like how similar adventure games done in this way do, there isnt really any incentive to replay them. However, there are also over 20 optional mini cases in between that you can do which can give you a couple more hours entertainment as you learn more about the little world the game is set in.