Halcyon Days ~Sunny Days with Sister-chan~ [v1.0.4] [CatNight]

May 8, 2026F95

You wash up on a quiet beach, barely conscious, only to be found and taken in by a kind-hearted nun known only as Sister-chan.
This is a cohabitation touch simulation game that gently unfolds your daily life together under the warmth of spring.

Thread Updated: 2026-05-07

Release Date: 2025-09-14

Original Name: Halcyon Days ~シスターちゃんと陽だまりの日々~

Developer: CatNight Ci-en – DLsite

Translator: ripno

Censored: Yes (Mosaics)

Version: 1.0.4

OS: Windows

Language: English (GLM-5)

Store: DLsite

Genre:

2DCG, Anal Sex, Censored, Corruption, Creampie, Groping, Internal view, Japanese Game, Male Domination, Male Protagonist, Masturbation, Oral Sex, Point & Click, Rape, Religion, Romance, Sexual Harassment, Sleep Sex, Teasing, Trainer, Vaginal sex, Virgin

Installation:

1. Extract and run.

Changelog:

v1.0.4

Fixed issue where relationship with Sister-chan would become extremely negative when going to town

【Bugs and Issues Under Investigation】

Unable to perform insertion during the second forced assault
creampie not counted when reaching climax simultaneously
Reverts back to calling “older brother”
We apologize for the inconvenience.

v1.0.3

Fixed ending not triggering
Fixed fewer choices appearing when climaxing simultaneously from behind
Fixed Sister-chan remaining asleep
Fixed remaining asleep when starting touching via “invite to H”

v1.0.2

Fixed receptivity being locked at 100
Fixed incorrect messages when walking in town
Fixed items being usable multiple times
Fixed 20,000-yen items not working correctly
Fixed Mamushi Drink not being released
Fixed character becoming depressed when inviting to H
Fixed insertion gauge not moving
Fixed unexpected messages during touch movement
Added wait time to touching to prevent crashes from rapid input

v1.0.1

Fixed screen darkening and progression halt when selecting “time to go home” on a day off
Fixed ending replaying after waking up in the morning
Fixed vaginal ejaculation count not increasing beyond one in erotic scenes

v1.0

Initial Release

Developer Notes:

Original Ci-en article

Regarding future updates

Hello everyone, this is Ando!

Today, I’d like to express my gratitude to everyone who purchased Halcyon Days ~Sunny Days with Sister-chan~, and share some details about our upcoming update plans.

Message of Gratitude

Thank you so much for playing my very first game. It brings me great joy to see so many people enjoying it, and I must admit, the response has exceeded my expectations. I will continue to work hard to meet your expectations. Thank you again for your continued support.

Future Update Plans

I’m sorry, but we do not plan to offer paid updates. Moving forward, we will focus on providing free updates to make the game even better. The following are the elements we plan to add in future updates:

Touching Scenes

Face-to-face sitting position (during sleep)
Cowgirl position
Scenario where you wash Sister-chan’s body in the bath
Oral service at the church (may be still images only)
Intimate scene at the church

Additional Character Portraits (Stand Art)

Add standing artwork for the town’s sister character
Add standing artwork for the receptionist
Add standing artwork for Sister-chan in her room

Additional Still Images

Add ending images
Add a scene of peeking into the bath
Add event stills for the town’s sister character and the receptionist

Apology Regarding Game Bugs

While we’ve received many kind messages saying things like “Sister-chan is so cute,” we’ve also received numerous reports about bugs in the game. I’m truly sorry that these issues have prevented you from enjoying a smooth gaming experience. To prevent this in the future, I plan to improve our debugging process.

Going forward, I won’t rely solely on my own playtesting. Instead, I’ll also commission freelance testers to conduct full playthroughs and utilize DLsite’s debugging services.

Ideally, I should have done this before the game’s release. However, since this was my first time developing and publishing a game, it didn’t occur to me to seek outside help. From now on, I’m committed to thoroughly improving our debugging efforts to avoid such issues.

Translator Notes:

I’m releasing an English translation patch for version 1.0.4 (2026.01.08).

The game has been re-translated using GLM-5.

A total of 116 images have been translated.

Default font: Asap Condensed Reguler.

Please enjoy the game, and feel free to share any feedback.

Since the encryption keys for all audio and image assets are different, this English patch will clearly not be compatible with version 1.0.2.

DOWNLOAD
Win: BUZZHEAVIER – GOFILE – PIXELDRAIN – VIKINGFILE – DATANODES

Thank you mortis_interessant for sharing the game!